Research ArticleSimulating Flow and Dispersion by Using WRF-CFD CoupledModel in a Built-Up Area of Shenyang China

Yijia Zheng1 Yucong Miao1 Shuhua Liu1 Bicheng Chen2 Hui Zheng1 and Shu Wang1

1Department of Atmospheric and Oceanic Sciences School of Physics Peking University Beijing 100871 China2Department of Meteorology The Pennsylvania State University University Park State College PA 16802 USA

Correspondence should be addressed to Shuhua Liu lshuhuapkueducn

Received 20 June 2014 Revised 21 October 2014 Accepted 5 November 2014

Academic Editor Bala Subrahamanyam

Copyright copy 2015 Yijia Zheng et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Results are presented from a series of numerical studies designed to investigate the atmospheric boundary layer structure ambientwind and pollutant source location and their impacts on the wind field and pollutant distribution within the built-up areasof Shenyang China Two models namely Open Source Field Operation and Manipulation (OpenFOAM) software packageand Weather Research and Forecasting (WRF) model are used in the present study Then the high resolution computationalfluid dynamics (CFD) numerical experiments were performed under the typical simulated atmospheric boundary conditionsIt was found that the atmospheric boundary structure played a crucial role in the pollution within the building cluster whichdetermined the potential turbulent diffusion ability of the atmospheric surface layer the change of the ambient wind direction cansignificantly affect the dispersion pattern of pollutants which was a more sensitive factor than the ambient wind speed under agiven atmospheric state the location of the pollution sources would dramatically determine the pollution patterns within built-upareasTheWRF-CFD numerical evaluation is a reliable method to understand the complicated flow and dispersion within built-upareas

1 Introduction

The air pollution within urban environments with densepopulation has become an important research issue in thepast two decades leading to numerous studies of the airflowand dispersion patterns around various building configu-rations Field measurements and laboratory-scale physicalmodeling such as water-tank or wind-tunnel experimentsare two traditional ways to study wind flow and dispersionprocess around buildings [1ndash8] However both these twomethods are costly which makes them difficult for practicalapplication

With rapid development in computer hardware andnumerical algorithms computational fluid dynamics (CFD)models have become common tools to simulating and pre-dicting flow and pollutant dispersion patterns in real built-up areas The CFD simulation method consists of solving thetransport (advection and diffusion) equation of concentra-tion based on the velocity field obtained from the Navier-Stokes equations CFD prognostic models can be classified

into three broad categories according to the respective tur-bulence closure schemes Reynolds-averaged NavierndashStokes(RANS) approach [9ndash12] Large-eddy simulation (LES) [13ndash15] and direct numerical simulation (DNS) approach Thechoice among these three methods is a balance between thecost and the goal In this study the RANS model will be usedbecause of its higher computational efficiency

Furthermore there are several studies that have numeri-cally examined the air flow and dispersion in built-up areasby using CFD models with boundary conditions given bymesoscale models Tewari et al demonstrated that by usingoutput of the WRF model as the initial and boundaryconditions the prediction ability of a CFD model employedover an urban area can be significantly improved [16] Liuet al investigated wind field and traffic pollutant dispersionat street level by coupling of LES in the local area withmesoscale atmospheric model WRF in the entire city [17]Miao et al coupled a CFD software package with a mesoscaleweather model WRF to studying the airflow and dispersionof pollutant in a complex urban area of Beijing China [18]

Hindawi Publishing CorporationAdvances in MeteorologyVolume 2015 Article ID 528618 15 pageshttpdxdoiorg1011552015528618

2 Advances in Meteorology

Shenyang located in Northeast China Plain is an impor-tant center of mineral and base of heavy industry of ChinaPollution managements have been performed during recentyears however air pollution remains a severe problem inShenyang compared to other cities Previous study performedby Miao et al [18] made a probe into studying and predictingurban flow and dispersion in densely built-up areas using aCFD model OpenFOAM coupled with a mesoscale modelWRF and just one case was carried on under unstableatmospheric boundary condition in summer In this studya series of sensitivity numerical experiments have beenperformed to study the sensitivity of factors associated withflow and dispersion process within the built-up area ofShenyang with high resolution such as the atmosphericboundary structure ambient wind direction and speed andthe location of the pollution sources using the coupledWRF-CFDmodel Furthermore an urban canopy parameterizationscheme was used inWRF simulation to better simulate urbanmeteorological conditions The study may support decision-making for pollution control strategies and traffic planning inShenyang

The remainder of the paper is organized as followsIn Section 2 the mesoscale model and CFD model weredescribed In Section 3 the setup of numerical experimentswas given And the results and discussions of the numericalexperiments were then presented in Section 4 and finally theconclusions were given in Section 5

2 Model Description and Coupling Method

21 Mesoscale Model A community model the WRF modelwas used in this study as a mesoscale model WRF is anonhydrostatic mesoscale model with several options fordynamic cores as well as various choices for physical param-eterizations In this study we used the Advanced ResearchWRF Version 34 which was released in April 2012 TheWRF model was used to simulate the wind and turbulencefields on urban scale whose horizontal dimension is fromtens of kilometers to hundreds of kilometers [19] The WRF-simulated results can be used to provide the boundaryconditions for the CFD model to recalculate flow fields forthe subdomain scale simulation [18 20] whose horizontaldimension is several kilometers [21]

22 CFD Model As a CFD model the Open Source FieldOperation and Manipulation (OpenFOAM) software pack-age version 211 which is a collection of C++ librarieswas used to solve complex problems in fluid mechanicsOpenFOAM is completely free distributed and allows userto develop some specific solvers which can be integratedwith already existing tools For further information aboutthe model please refer to the Programmerrsquos Guide availablewith OpenFOAM [22] In this study we used the solversimpleFoam one of the standard solvers in OpenFOAM

The simpleFoam solver which is a steady-state solverfor incompressible and turbulent flow is used to solve theReynolds-averaged Navier-Stokes (RANS) equations withthe standard 119896-120576 turbulence model by using the SIMPLE

scheme [23] The SIMPLE scheme is an iterative method tosolve algebraic system of equations A termination criterionof 10minus4 is used for all field variables in this study A briefintroduction of iterative procedure of the SIMPLE methodcan be found in Miao et al [20]

Step 1 Set up the initial guess field of pressure and velocity

Step 2 Solve the momentum equation to compute the inter-mediate velocity field

Step 3 Solve the pressure equation

Step 4 Correct the velocities on the basis of the new pressurefield

Step 5 Update the guess fields of pressure and velocity

Step 6 Repeat Steps 2 to 5 until convergence

3 Numerical Experiments Setup

31 WRF Simulation Setup TheWRF model was configuredwith 3 two-way interactive nested grids with horizontalgrid spacing of 375 75 and 15 km and horizontal griddimensions were 40 times 40 56 times 46 and 51 times 51 respectively(Figure 1(a)) The innermost domain was set with the centerlocated at 4177∘N 12341∘E and covered most of Shenyangand its adjacent areas (Figure 1(b)) In the vertical directionwe used 28 atmospheric eta levels ranging from surface upto 50 hPa There were 14 levels within the lowest 2 km inthe atmosphere to better resolve the atmospheric boundarylayer structureThe initial conditionswere obtained from 1∘ times1∘ Final Operational Global Analysis (FNL) data producedby the NCEP (National Centers for Environmental Predic-tion) every 6 hours which was adopted as the backgroundmeteorological data fields Since the typical features (ieboundary layer height and evolution process) of the atmo-spheric boundary layer structures of different seasons weredifferent two 42-h WRF numerical experiments (Summer-Run and Winter-Run) were designed The details of the twoWRF simulations are listed in Table 1 There were no obvioussynoptic systems over northern China during the two WRF-simulated periods

The land use dataset based onModerate Resolution Imag-ing Spectroradiometer (MODIS) was used in this study inwhich 20 land use categories were included and the land usecategory of the innermost domain was shown in Figure 1(b)We used the Mellor-Yamada-Janjic PBL scheme [24 25]which was capable of predicting TKE Other physical optionschosen were the Rapid Radiative Transfer Model (RRTM)long-wave scheme [26] the Dudhia shortwave scheme [27]the WRF Single-Moment (WSM) 3-class simple ice scheme[28] Kain-Fritsch (new eta) scheme [29] and the Noah land-surface scheme [30] with a single-layer UCM (Urban CanopyModel) [31 32] The first 16 hours of the simulations wereused as spin-up and WRF output interval was set to 1 hourThe coupling method of Miao et al [18 20] is used to couple

Advances in Meteorology 3

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(a)

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Other

Water

Forest

Grassland

Cropland

Urban

(b)

Figure 1 Nested computational domains and the land use category of the innermost domain in the WRF model simulation (a) nestedcomputational domains in the WRF model simulation (b) the land use category of the innermost domain of the WRF model Crosses showthe location of the meteorological observatories

Table 1 Run-time domain configurations and physics options usedin the WRF simulation

Run-time domain configurations andphysics options

Summer-Run From 0800 LST 12 August to 0200 LST 14August 2012

Winter-Run From 0800 LST 15 February to 0200 LST17 February 2012

Domain dimensions 40 times 40 56 times 46 and 51 times 51Grid size 375 75 and 15 kmLand use dataset MODISMicrophysics scheme WSM-3

Radiation scheme RRTM long-wave and Dudhia short-wavescheme

Cumulus scheme Kain-Fritsch (new eta) schemePBL scheme MYJLand surface scheme Noah with single-layer UCM

WRF and OpenFOAM The validations of OpenFOAM canbe found at the study of Miao et al [18 20]

32 CFD Simulation Setup The CFD model simulationdomain covers a part of Northeastern University Chinalocated at the center of Shenyang A Google Earth image andthe CFD model domain with horizontal building configura-tion at the surface were shown in Figure 2 The actual build-ings and their different shapes were simplified to cuboidsand the average height of the buildings was 245m with thetallest and lowest building being 81m and 6mThehorizontalgrid interval was 10m and the horizontal grid dimensionwas 86 times 81 In the vertical a nonuniform grid system with

50 levels was employed in which the vertical grid intervalwas 5m up to the 30th level and the grid interval of thetopmost 20 levels was 10mTheWRF data from one grid thatwas nearest to the location of the CFD domain was used toprovide initial and boundary conditions to OpenFOAMThevelocity components and TKE at the inflow condition canbe directly given by WRF simulation while the momentumdiffusion coefficient was indirectly calculated by Grisogonoscheme [33 34] and the TKEdissipation rate is parameterizedby using these two parameters

120576 =119862120583

1198962

]119905

(1)

where 119896 is the TKE 120576 is its dissipation rate ]119905

is the turbulentexchange coefficient and 119862

120583

is an empirical constant Tosimulate the wind and turbulent fields of different situationthe initial and boundary conditions of velocity componentsand TKE were set by the simulation of WRF of differentmoments (ie 1400 LST and 2200 LST) The zero-gradientboundary conditionwas employed at the outflow boundariesincluding the top boundary The building surface was set asbeing in a no-slip condition and thewall turbulence functionswere employed to the grid points adjacent to the walls [35]

Three point sources located at different places were hypo-thetically set on the ground level in the built-up area whichwere continuously emitted during the simulation periodThelocations of the two point sources are shown in Figure 2(b)labeled by the crosses one was set at the southern side ofbuilding-A whose height was 81m the other one was set inthe center of build-up area The emission rate of each sourcewas 10 ppm sminus1 and the time step was set to 1 s A seriesof sensitivity studies have been performed resulting in thatthe concentration pattern was stable when the number ofintegral steps reached 5000 and thus the total number of the

4 Advances in Meteorology

(a)

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Figure 2 Google Earth image and the horizontal plane of the CFD computation domain (a) Google Earth image of Northeastern University(b) the horizontal plane of the CFD computation domain at 119911 = 25mThe red rectangle in (a) indicates the CFD domain the crosses labeledby P1 and P2 in (b) indicate the locations of point sources

50∘N

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(b)

Figure 3 The observed sea level pressure field at (a) 0800 LST 16th of February 2012 and (b) 0800 LST 13th of August 2012

integrate steps was set to 7000 for all the dispersion numericalexperiments

4 Results and Discussions

In this section the two series numerical experiments of theWRF-CFD coupled model on winter and summer would bepresented

41 Simulation Results in Winter

411 Simulation of WRF Winter Experiment Figure 3(a)showed the observed sea level pressure field at 0800 LST 16February 2012 At this time the observed sea level pressurefield exhibited a high pressure system over the Mongoliaregion and a low pressure system over the sea of OkhotskShenyang was located in the uniform pressure field in front ofMongolia high circulation without obvious synoptic system

Severe air pollution often happens in this situation overShenyang area [36]

The measurements from 17 meteorological observatories(Figure 1(b)) located in Shenyang area were used to examinethe accuracy of theWRFmodel Figure 4 showed the diurnalvariations of average observed and WRF-simulated 2-mtemperature and 10-m speed Both the observation and simu-lation are the mean value of the 17 stations or correspondinggrids It is noted that the observed temperature was higherthan simulated one during the winter which was the heatingseason of Shenyang area (Figure 7(a)) This difference mayowe to the underestimation of the anthropogenic heat inWRF As noted in earlier studies the anthropogenic heat haslarger impact on surface air temperature in winter than insummer [37] Despite this deficiency the diurnal temperaturecycle was replicated well by WRF model The accuracy ofwind speed simulation was lower than temperature thesimulated wind speed was higher than observed one This

Advances in Meteorology 5

0200 0600 1000 1400 1800 2200February 16th (hour)

0

minus5

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(a)

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Figure 4 Time series of observed and WRF-simulated results (a c) 2-m temperature (b d) 10-m wind speed (a b) simulation on 16February 2012 (c d) simulation on 13 August 2012 The observation is the mean value of 17 meteorological stations around Shenyang whilethe simulation is the average of the values taken at the grids nearest to the stations

is a general tendency by the model to overestimate windspeed found in many earlier studies [38ndash40] A new methodto parameterize the effects that the unresolved topographyexerts over the surface circulations has been implementedin WRFv341+ to correct the high wind speed bias [40] Inaddition the large anthropogenic heat in winter may alsocontribute to the difference between simulated and observedwind speed

Figure 5 exhibited the 10-m wind vector fields and 2-mtemperature fields of the innermost WRF domain on 16thof February 2012 During the studied period the northwestwind dominated the Shenyang area and the wind becameweaker when the ground temperature gets higher Further-more we found that the wind speed in the urban areaof Shenyang was lower than the suburb areas which wasparticularly obvious at 1000 LST and 1400 LST At 2200 LSTthe wind in the southeast off the city turned to the west

Temperature stratification and boundary layer height aretwo important meteorological factors related to pollutantdispersion process Temperature stratification affects verticaldispersion of air pollutant in atmospheric boundary layerand low-level inversion which trapped humidity and pollu-tant is a key factor affecting regional air qualityThe boundarylayer height determines the volume of air which can be usedto dilute pollutants The WRF-simulated potential tempera-ture profile and height-time section of potential temperatureat the grid cell that was nearest to the location of the CFDdomain in WRF were given in Figure 6 The MYJ schemedetermines the PBL height using the TKE profile Since the

TKE is largest within the PBL MYJ defines the top of thePBL to be the height where the TKE decreases to a prescribedlow value [41] which leads to unreliable results during winternight Instead the diurnal variation of boundary layer heightcalculated using the 15-theta-increase method was shown inFigure 6 The 15-theta-increase method defines PBL heightsas the level at which the potential temperature first exceedsthe minimum potential temperature within the boundarylayer by 15 K [42 43] The weak inversion can be seen at0400 LST and the surface layer began to turn into the mixedlayer at 0800 LST at 2000 LST the inversion was formedagain because of the cooling of surface (Figure 6(a)) As wasshown in Figure 6(e) we can clearly see that the inversionwas formed at around 1700 LST and lasted the whole nightFurthermore the boundary layer height (mixed layer height)of the periods in which the inversion existed was lowerthan any other time of the day (Figure 6(c)) which was notgood for the vertical diffusion of pollutant released from theground

412 Simulation of CFDExperiments inWinter According tothe analysis of WRF simulation results two CFD numericalexperiments with different atmospheric boundary conditions(unstable and stable) at differentmoments were set up that is1400 LST and 2200 LST At 1400 LST an unstable mixed layerwas fully developed and reached the highest boundary layerheight (about 18 km) of the winter simulation period andthis unstable boundary structure was good for the verticalmixing process of the pollutant On the contrary a typical

6 Advances in Meteorology

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(a)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

minus16

minus15

minus14

minus13

minus12

minus11

minus10

minus9

minus86

Reference vector

Tem

pera

ture

2m

(∘C)

(b)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N123

∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(c)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

minus16

minus15

minus14

minus13

minus12

minus11

minus10

minus9

minus8

6

Reference vector

Tem

pera

ture

2m

(∘C)

(d)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

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998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(e)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

minus16

minus15

minus14

minus13

minus12

minus11

minus10

minus9

minus86

Reference vectorTe

mpe

ratu

re2

m (∘

C)

(f)

Figure 5The 10-m wind vector fields and 2-m temperature fields of Shenyang on 16th of February 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

Advances in Meteorology 7

08 LST04 LST

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0

255 258 261 264 267 270 273

Hei

ght (

m)

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(a)

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Potential temperature (K)285 288 291 294 297 300 303 306

08 LST04 LST

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(b)

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(K)

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ght (

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0 4 8 12 16 20

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ture

(K)

(f)

Figure 6 The simulated boundary layer structure of WRF (a b) potential temperature profile (c d) diurnal variation of boundary layerheight (e f) height-time section of potential temperature (a c e) simulation on 16 February 2012 (b d f) simulation on 13 August 2012

8 Advances in Meteorology

A

600

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)

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(a)

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01

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(d)

Figure 7 Simulated concentration (ppm) and wind vector fields at 1400 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

stable nocturnal boundary layer was established at 2200 LSTwith a lower boundary layer height (about 300 m)

Figure 7 exhibited the simulated concentration (ppm)and wind vector fields for two heights at 1400 LST on 16th ofFebruary At this moment the ambient wind direction givenby the WRF model was northwest and the speed was about35m sminus1 both at 119911 = 25m and 119911 = 225m At 119911 = 25mwind vectors within the buildings were quite different fromthe free wind vectors on the boundary regions under theinfluences of the buildings It was particularly obvious in thesouthern part of the build-up regions where the distributionof the buildings was denser than the other areas When theairflow passed through the building-A two lee side vortexeswere established a strong one was on the southern lee sideof the building-A and the other weak one was on the eastAnd wind speed around the edge of building-A was fastest inthe build-up area Since the building distribution was sparser

at the height of 225m the wind field there was strongerand simpler The two vortexes still existed on the lee sideof building-A Besides that at the height of 225m most ofwind vectors within the building followed the ambient winddirection

At 119911 = 25m when the point source was located at P1driven by the vortex on the lee side of building-A a pollutantplume with concentrations higher than 5 ppm extended asan ellipse-pattern and most of the pollutants were dispersedtoward the southeast (Figure 7(a)) The point source P2 waslocated at a more open area thus the pollutant concentrationwas high only at the southeast of the source due to theblock effect of the building there (Figure 7(b)) Similar to thewind vector fields the concentration field at 119911 = 225m wassimpler than that of lower level most of the pollutants weretransported by the ambient wind direction

Advances in Meteorology 9

A

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Figure 8 Simulated concentration (ppm) and wind vector fields at 2200 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

At 2200 LST a typical nocturnal stable layer was formednear the surface (Figure 6(e)) which may inhibit the dis-persion process of pollutants Although the ambient windspeed of 2200 LST was higher than that of 1400 LST thepollution could be more serious at 2200 LST with the samepoint source For example in the P1 point source experimentthe polluted area with concentration higher than 01 ppmwassmaller at night (Figures 8(a) and 8(c)) which reflected thatthe diffusion ability was weaker at that moment and morepollutants were trapped in the vortex on the leeward side ofbuilding-A

For the P2 point source experiment as the wind speedincreased the shape of pollution plume was changed a littleand at the height of 25m more pollutants were transportedalong the channel formed by the buildings located on thenorth of P2 Unlike P1 placing on the leeward side building

the P2 point source was set up in a more open area the pollu-tion of P2 was dominated by the convection process ratherthan the turbulent diffusion process Therefore comparingto the daytime unstable situation as wind speed increasedthe convection of the pollutants strengthened and then thepollution was relaxed a little at night (Figures 8(b) and 8(d))

In short it was found that buildings may alter the flowand concentration fields significantly The position of thepoint source had significant influences on the concentrationpattern Comparing the flow and dispersion pattern at twomoments it was found that the convection and turbulentdiffusion were the two important processes to determinethe pollution serious level Within the nocturnal stableatmospheric boundary structure although the ambient windspeed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

10 Advances in Meteorology

42 Simulation Results in Summer

421 Simulation of WRF Summer Experiment Figure 3(b)showed the observed sea level pressure field at 0800 LST 13August 2012 Similar to the winter case the Shenyang areawas under the control of this high pressure system with weaksynoptic system

Figures 4(c) and 4(d) exhibited the diurnal variationsof the observed and simulated 2-m temperature and 10-mwind speed to examine the WRF output The simulatedtemperature was a little lower than observed one at nightand the temperature during the daytime was simulated wellDespite the fact that the simulated wind speed was slightlyhigher the diurnal variation of the wind speed was simulatedwell On the whole the simulation result in summer wasbetter than that in winter

The 10-m wind vector fields and 2-m temperature fieldsof the innermost WRF domain on 16th of February 2012were shown in Figure 9 At 0200 LST the main directionof the wind was northeast while the wind turned to northat 0600 LST The wind speed increased as the land surfacewas heated by the sun It was noted that at 1800 LST thewind direction within the built-up areas of Shenyang wasdifferent from that in the suburb area the wind in the built-up areas was northwestern while the wind in the suburb areawas northern At 2200 LST the wind turned to north in thesimulation region We can also obviously find the urban heatisland effect in Shenyang at 0200 LST 1800 LST and 2200 LSTthe 2-m temperature over the built-up area was significantlyhigher than that of the suburb area

The potential temperature profile height-time section ofthe potential temperature profile and time series of boundarylayer height simulated by WRF were given in Figure 6 Thesurface-based inversion formed at 0400 LST and the intensityof inversion below the height of 500m was 23 K per 100mheight which was stronger than the inversion that happenedin winter at the same time and the depth of the inversionlayer was also thicker than that of winter (Figures 6(a) and6(b)) At 0800 LST since the ground was warmed by thesunlight a thin mixed layer was generated near ground andthe temperature inversion was detached from the ground atthe height of 250m After 0800 LST the low-level inversionlayer disappeared gradually at 1200 LST a mixed layer wasformed in the lower atmosphere from ground to the heightof 700m (Figure 6(b)) In the afternoon the mixed layerextended well to 15 km height (Figure 6(d)) favoring thevertical dilution of pollutant At night the ground was cooledby the nocturnal radiation causing the generation of theinversion stable layer near the ground Comparing to thenocturnal stable layer of the winter case the boundary layerheight of the summer experiment was lower from 0000 LSTto 0600 LST because of the calm ambient wind background(Figures 6(c) and 6(d))

422 Simulation of CFD Experiments in Summer Similarto the winter CFD numerical experiments two experi-ments with different atmospheric boundary structures weredesigned at 1400 LST (unstable case) and 2200 LST (stablecase)

Figure 10 illustrated the simulated concentration (ppm)and wind vector fields at different height at 1400 LST on 13thof August when the ambient wind direction was north Itwas noted that two counterclockwise vortices formed behindbuilding-A which was a typical double-eddy circulationreported by Hunter et al [44] and Zhang et al [45] Compar-ing to the wind vector field at 119911 = 25m the wind vector fieldof 225mwasmuch simpler and the north flowwas dominantin most of the region

At the lower level the distributions of pollutant concen-tration were consistent with the flow patternWhen the pointsourcewas located at P1 or P2 the pollutantswere transportedand trapped in the circulations of the two vortexes behindbuilding-A

Comparing the concentration fields of point sourcesP1 and P2 at two heights it was interesting to find thatthe concentration within the red rectangle in Figure 10 washigher at the height of 225m than the lower level (25mheight) The phenomenon can be explained by the windfields at different height At the height of 25m since redrectangle region was surrounded by buildings where thewind fields were detached from the ambient boundary windand were dominant by the east wind therefore the pollutantreleased from the northern P1 and P2 point sources cannotbe transported to this region directly In the contrary at theheight of 225m the red rectangle regionwas dominant by thenorth wind therefore the pollutant can be easily transportedthere

At 2200 LST when the south ambient wind blew a quitedifferent flow pattern was presented within the built-up area(Figure 11) compared to that of 1400 LST A strong divergencezone can be found in the south of building-A at the heightof 25m indicated by the red dashed rectangle in Figure 11When the airflowblew from the south a typical step-up notchwas formed by building-A (81m) and building-B (24m) asthe vertical wind field presented in Figure 12 the south inletwind was blocked by the taller building (building-A) anddescended along the windward wall of building-A and thendiverged near the ground

At the lower level the wind field around the point sources(P1 and P2) was totally rearranged by the effects of thebuildings around At the height of 225m since the sparserbuilding distribution the wind field was more close to theambient wind Therefore the wind fields of the height of25m and 225m were quite different as well as the pollutantdistributions At 119911 = 25m most of the pollutant releasedfrom P1 and P2 source was transported to south by thedivergence zone formed on the south side building-A

In these two cases it was found that the change of theambient wind direction can significantly affect the flow fieldsand pollutant distributions within the building cluster

5 Discussion and Conclusions

This study examined urban airflow and dispersion patternof pollutant released from hypothetical sources in North-eastern University of Shenyang China by using a WRF-CFD coupled model Two WRF numerical experiments

Advances in Meteorology 11

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(a)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(b)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(c)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(d)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(e)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(f)

Figure 9 The 10-m wind vector fields and 2-m temperature fields of Shenyang on 13th of August 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

12 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

(c)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

01

05

1

25

5

10

20

35

50

(d)

Figure 10 Simulated concentration (ppm) and wind vector fields at 1400 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

(Summer-Run and Winter-Run) were performed to studythe typical features of the atmospheric boundary layer struc-tures of different season Then the coupled WRF-CFD wasused to study how the atmospheric boundary structureambient wind and source position affect the wind fieldand pollutant distribution within the built-up areas It wasfound that the pollutant dispersion pattern and the pollutiondegree dispersion were complicated in the presence of realbuilding clusters and under varying atmospheric bound-ary structures ambient wind and locations of pollutionsources

From this preliminary numerical study it was found thatthe atmospheric boundary structure played a crucial role onthe pollution within the building cluster which determinedthe potential turbulent diffusion ability of the atmosphericsurface layer For example within a nocturnal stable atmo-spheric boundary condition although the ambient wind

speed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

The change of the ambient wind direction can signifi-cantly affect the dispersion pattern of pollutants which was amore sensitive factor than the ambient wind speedThereforewhen a building cluster was designed it was important toconsider the frequency of the ambient wind direction there

Under a given atmospheric state the location of thepollution source would dramatically determine the pollutionpatterns within the built-up areasWhen the pollutant sourcewas set up on the leeward side of the building the pollutantdispersion pattern was dominated by turbulent diffusion pro-cess which was affected by atmospheric boundary structureswhile the convection process dominated when the pollutantsource was set up in a more open area Besides that thedistribution of pollutant concentrationwas driven by the flowpattern

Advances in Meteorology 13

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

A

B

3

Reference vector

A

B

(a)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

B

(b)

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

A

(c)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

(d)

Figure 11 Simulated concentration (ppm) and wind vector fields at 2200 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

A

B

90

60

30

0

Z(m

)

Y (m)6005004003002001000

Reference vector3

Figure 12 The vertical plane of the wind vector field across 119883 =325m

Finally it should be noted that the wind fields anddispersion patterns within the building clusters were com-plicated which cannot be obtained from the ambient wind

TheWRF-CFD numerical evaluation can be used as a reliablemethod to understand the complicated flow and dispersionwithin the built-up areas

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is supported by the China Meteorological Admin-istration Special Public Welfare Research Fund under Grantno GYHY201106033 and the National Natural Science Foun-dation of China under Grant no 41175004

14 Advances in Meteorology

References

[1] H R Olesen R Berkowicz M Ketzel and P Loslashfstroslashm ldquoVal-idation of OML AERMODPRIME and MISKAM using theThompson wind-tunnel dataset for simple stack-building con-figurationsrdquo Boundary-LayerMeteorology vol 131 no 1 pp 73ndash83 2009

[2] R S Thompson ldquoBuilding amplification factors for sourcesnear buildings a wind-tunnel studyrdquo Atmospheric EnvironmentPart A General Topics vol 27 no 15 pp 2313ndash2325 1993

[3] A F Stein and B M Toselli ldquoStreet level air pollution in Cor-doba City ArgentinardquoAtmospheric Environment vol 30 no 20pp 3491ndash3495 1996

[4] RWMacDonald R F Griffiths and S C Cheah ldquoField exper-iments of dispersion through regular arrays of cubic structuresrdquoAtmospheric Environment vol 31 no 6 pp 783ndash795 1997

[5] R W Macdonald R F Griffiths and D J Hall ldquoA comparisonof results from scaled field and wind tunnel modelling ofdispersion in arrays of obstaclesrdquoAtmospheric Environment vol32 no 22 pp 3845ndash3862 1998

[6] M Pavageau andM Schatzmann ldquoWind tunnel measurementsof concentration fluctuations in an urban street canyonrdquo Atmo-spheric Environment vol 33 no 24-25 pp 3961ndash3971 1999

[7] P Kastner-Klein and E J Plate ldquoWind-tunnel study of concen-tration fields in street canyonsrdquo Atmospheric Environment vol33 no 24-25 pp 3973ndash3979 1999

[8] I Mavroidis R F Griffiths and D J Hall ldquoField and windtunnel investigations of plume dispersion around single surfaceobstaclesrdquo Atmospheric Environment vol 37 no 21 pp 2903ndash2918 2003

[9] DDelaunay D Lakehal C Barre andC Sacre ldquoNumerical andwind tunnel simulation of gas dispersion around a rectangularbuildingrdquo Journal ofWind Engineeringamp Industrial Aerodynam-ics vol 67-68 pp 721ndash732 1997

[10] I R Cowan I P Castro and A G Robins ldquoNumericalconsiderations for simulations of flow and dispersion aroundbuildingsrdquo Journal of Wind Engineering and Industrial Aerody-namics vol 67-68 pp 535ndash545 1997

[11] J J Baik and J J Kim ldquoOn the escape of pollutants from urbanstreet canyonsrdquo Atmospheric Environment vol 36 no 3 pp527ndash536 2002

[12] K Nazridoust and G Ahmadi ldquoAirflow and pollutant transportin street canyonsrdquo Journal of Wind Engineering and IndustrialAerodynamics vol 94 no 6 pp 491ndash522 2006

[13] Y Tominaga SMurakami andAMochida ldquoCFDprediction ofgaseous diffusion around a cubic model using a dynamic mixedSGSmodel based on composite grid techniquerdquo Journal ofWindEngineering and Industrial Aerodynamics vol 67-68 pp 827ndash841 1997

[14] K Sada and A Sato ldquoNumerical calculation of flow andstack-gas concentration fluctuation around a cubical buildingrdquoAtmospheric Environment vol 36 no 35 pp 5527ndash5534 2002

[15] X-X Li C-H Liu and D Y C Leung ldquoLarge-eddy simulationof flow and pollutant dispersion in high-aspect-ratio urbanstreet canyons with wall modelrdquo Boundary-Layer Meteorologyvol 129 no 2 pp 249ndash268 2008

[16] M Tewari H Kusaka F Chen et al ldquoImpact of couplinga microscale computational fluid dynamics model with amesoscale model on urban scale contaminant transport anddispersionrdquo Atmospheric Research vol 96 no 4 pp 656ndash6642010

[17] Y S Liu S G Miao C L Zhang G X Cui and Z S ZhangldquoStudy on micro-atmospheric environment by coupling largeeddy simulation with mesoscale modelrdquo Journal of Wind Engi-neering amp Industrial Aerodynamics vol 107-108 pp 106ndash1172012

[18] Y Miao S Liu B Chen B Zhang S Wang and S Li ldquoSimu-lating urban flow and dispersion in Beijing by coupling a CFDmodel with theWRFmodelrdquoAdvances in Atmospheric Sciencesvol 30 no 6 pp 1663ndash1678 2013

[19] X Fang W Jiang S Miao et al ldquoThe multi-scale numericalmodeling system for research on the relationship betweenurban planning and meteorological environmentrdquo Advances inAtmospheric Sciences vol 21 no 1 pp 103ndash112 2004

[20] Y C Miao S H Liu H Zheng et al ldquoA multi-scale urbanatmospheric dispersion model for emergency managementrdquoAdvances in Atmospheric Sciences vol 31 no 6 pp 1353ndash13652014

[21] S Miao W Jiang X Wang and W Guo ldquoImpact assessmentof urban meteorology and the atmospheric environment usingurban sub-domain planningrdquoBoundary-LayerMeteorology vol118 no 1 pp 133ndash150 2006

[22] OpenCFD OpenFOAM The Open Source Computational FluidDynamics (CFD) Toolbox 2008 httpwwwopencfdcoukopenfoam

[23] J H Ferziger and M Peric Computational Methods for FluidDynamics Springer Berlin Germany 3rd edition 2001

[24] Z I Janjic ldquoThe step-mountain coordinate physical packagerdquoMonthly Weather Review vol 118 no 7 pp 1429ndash1443 1990

[25] Z I Janjic ldquoThe step-mountain eta coordinate model furtherdevelopments of the convection viscous sublayer and turbu-lence closure schemesrdquoMonthlyWeather Review vol 122 no 5pp 927ndash945 1994

[26] E J Mlawer S J Taubman P D Brown M J Iacono and S AClough ldquoRadiative transfer for inhomogeneous atmospheresRRTM a validated correlated-k model for the longwaverdquoJournal of Geophysical Research Atmospheres vol 102 no 14pp 16663ndash16682 1997

[27] J Dudhia ldquoNumerical study of convection observed dur-ing the winter monsoon experiment using a mesoscale two-dimensionalmodelrdquo Journal of theAtmospheric Sciences vol 46no 20 pp 3077ndash3107 1989

[28] S-Y Hong J Dudhia and S-H Chen ldquoA revised approach toice microphysical processes for the bulk parameterization ofclouds and precipitationrdquoMonthlyWeather Review vol 132 no1 pp 103ndash120 2004

[29] J S Kain ldquoThe Kain Fritsch convective parameterization anupdaterdquo Journal of Applied Meteorology vol 43 no 1 pp 170ndash181 2004

[30] F Chen and J Dudhia ldquoCoupling and advanced land surface-hydrology model with the Penn State-NCAR MM5 modelingsystem Part I model implementation and sensitivityrdquoMonthlyWeather Review vol 129 no 4 pp 569ndash585 2001

[31] H Kusaka H Kondo Y Kikegawa and F Kimura ldquoA simplesingle-layer urban canopy model for atmospheric modelscomparison with multi-layer and slab modelsrdquo Boundary-LayerMeteorology vol 101 no 3 pp 329ndash358 2001

[32] H Kusaka and F Kimura ldquoCoupling a single-layer urbancanopy model with a simple atmospheric model impact onurban heat island simulation for an idealized caserdquo Journal of theMeteorological Society of Japan vol 82 no 1 pp 67ndash80 2004

Advances in Meteorology 15

[33] B Grisogono and J Oerlemans ldquoJustifying the WKB approxi-mation in pure katabatic flowsrdquo Tellus A Dynamic Meteorologyand Oceanography vol 54 no 5 pp 453ndash462 2002

[34] A Jericevic L Kraljevic B Grisogono H Fagerli and Z Vece-naj ldquoParameterization of vertical diffusion and the atmosphericboundary layer height determination in the EMEP modelrdquoAtmospheric Chemistry and Physics vol 10 no 2 pp 341ndash3642010

[35] C Bicheng L ShuhuaM Yucong et al ldquoConstruction and vali-dation of a computational fluid dynamics approach for flow anddispersion modeling in urban areardquo Journal of MeteorologicalResearch vol 27 no 6 pp 923ndash941 2013

[36] C Liqiang and Y Hongbin ldquoSynoptic patterns of regional airpollution in Liaoning Provincerdquo Environmental Pollution ampControl vol 28 no 6 pp 435ndash451 2006 (Chinese)

[37] S A Adachi H KusakaM G Duda et al ldquoImprovement of thesingle-layer UCM in the WRF modelrdquo in Proceedings of the 8thInternational Conference on Urban Climates (ICUC8 rsquo12) 2012

[38] G Roux Y Liu L D Monache et al ldquoVerification of highresolution WRF-RTFDDA surface forecasts over mountainsand plainsrdquo Proceedings of the 10th WRF Usersrsquo Workshop pp20ndash23 2009

[39] S Shimada T Ohsawa S Chikaoka et al ldquoAccuracy of the windspeed profile in the lower PBL as simulated by theWRFmodelrdquoSola vol 7 pp 109ndash112 2011

[40] P A Jimenez and J Dudhia ldquoImproving the representation ofresolved and unresolved topographic effects on surface wind inthe wrf modelrdquo Journal of AppliedMeteorology and Climatologyvol 51 no 2 pp 300ndash316 2012

[41] Z I Janjic ldquoNonsingular implementation of theMellor-Yamadalevel 25 scheme in the NCEP Meso modelrdquo NOAANWSNCEP Office Note 437 2001

[42] X-M Hu J W Nielsen-Gammon and F Zhang ldquoEvaluationof three planetary boundary layer schemes in the WRF modelrdquoJournal of Applied Meteorology and Climatology vol 49 no 9pp 1831ndash1844 2010

[43] J W Nielsen-Gammon C L Powell M J Mahoney et alldquoMultisensor estimation of mixing heights over a coastal cityrdquoJournal of Applied Meteorology and Climatology vol 47 no 1pp 27ndash43 2008

[44] L J Hunter G T Johnson and I D Watson ldquoAn investigationof three-dimensional characteristics of flow regimes withinthe urban canyonrdquo Atmospheric Environment Part B UrbanAtmosphere vol 26 no 4 pp 425ndash432 1992

[45] Y Q Zhang S P Arya and W H Snyder ldquoA comparisonof numerical and physical modeling of stable atmosphericflow and dispersion around a cubical buildingrdquo AtmosphericEnvironment vol 30 no 8 pp 1327ndash1345 1996

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

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Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

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MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

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Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Geological ResearchJournal of

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Geology Advances in

2 Advances in Meteorology

Shenyang located in Northeast China Plain is an impor-tant center of mineral and base of heavy industry of ChinaPollution managements have been performed during recentyears however air pollution remains a severe problem inShenyang compared to other cities Previous study performedby Miao et al [18] made a probe into studying and predictingurban flow and dispersion in densely built-up areas using aCFD model OpenFOAM coupled with a mesoscale modelWRF and just one case was carried on under unstableatmospheric boundary condition in summer In this studya series of sensitivity numerical experiments have beenperformed to study the sensitivity of factors associated withflow and dispersion process within the built-up area ofShenyang with high resolution such as the atmosphericboundary structure ambient wind direction and speed andthe location of the pollution sources using the coupledWRF-CFDmodel Furthermore an urban canopy parameterizationscheme was used inWRF simulation to better simulate urbanmeteorological conditions The study may support decision-making for pollution control strategies and traffic planning inShenyang

The remainder of the paper is organized as followsIn Section 2 the mesoscale model and CFD model weredescribed In Section 3 the setup of numerical experimentswas given And the results and discussions of the numericalexperiments were then presented in Section 4 and finally theconclusions were given in Section 5

2 Model Description and Coupling Method

21 Mesoscale Model A community model the WRF modelwas used in this study as a mesoscale model WRF is anonhydrostatic mesoscale model with several options fordynamic cores as well as various choices for physical param-eterizations In this study we used the Advanced ResearchWRF Version 34 which was released in April 2012 TheWRF model was used to simulate the wind and turbulencefields on urban scale whose horizontal dimension is fromtens of kilometers to hundreds of kilometers [19] The WRF-simulated results can be used to provide the boundaryconditions for the CFD model to recalculate flow fields forthe subdomain scale simulation [18 20] whose horizontaldimension is several kilometers [21]

22 CFD Model As a CFD model the Open Source FieldOperation and Manipulation (OpenFOAM) software pack-age version 211 which is a collection of C++ librarieswas used to solve complex problems in fluid mechanicsOpenFOAM is completely free distributed and allows userto develop some specific solvers which can be integratedwith already existing tools For further information aboutthe model please refer to the Programmerrsquos Guide availablewith OpenFOAM [22] In this study we used the solversimpleFoam one of the standard solvers in OpenFOAM

The simpleFoam solver which is a steady-state solverfor incompressible and turbulent flow is used to solve theReynolds-averaged Navier-Stokes (RANS) equations withthe standard 119896-120576 turbulence model by using the SIMPLE

scheme [23] The SIMPLE scheme is an iterative method tosolve algebraic system of equations A termination criterionof 10minus4 is used for all field variables in this study A briefintroduction of iterative procedure of the SIMPLE methodcan be found in Miao et al [20]

Step 1 Set up the initial guess field of pressure and velocity

Step 2 Solve the momentum equation to compute the inter-mediate velocity field

Step 3 Solve the pressure equation

Step 4 Correct the velocities on the basis of the new pressurefield

Step 5 Update the guess fields of pressure and velocity

Step 6 Repeat Steps 2 to 5 until convergence

3 Numerical Experiments Setup

31 WRF Simulation Setup TheWRF model was configuredwith 3 two-way interactive nested grids with horizontalgrid spacing of 375 75 and 15 km and horizontal griddimensions were 40 times 40 56 times 46 and 51 times 51 respectively(Figure 1(a)) The innermost domain was set with the centerlocated at 4177∘N 12341∘E and covered most of Shenyangand its adjacent areas (Figure 1(b)) In the vertical directionwe used 28 atmospheric eta levels ranging from surface upto 50 hPa There were 14 levels within the lowest 2 km inthe atmosphere to better resolve the atmospheric boundarylayer structureThe initial conditionswere obtained from 1∘ times1∘ Final Operational Global Analysis (FNL) data producedby the NCEP (National Centers for Environmental Predic-tion) every 6 hours which was adopted as the backgroundmeteorological data fields Since the typical features (ieboundary layer height and evolution process) of the atmo-spheric boundary layer structures of different seasons weredifferent two 42-h WRF numerical experiments (Summer-Run and Winter-Run) were designed The details of the twoWRF simulations are listed in Table 1 There were no obvioussynoptic systems over northern China during the two WRF-simulated periods

The land use dataset based onModerate Resolution Imag-ing Spectroradiometer (MODIS) was used in this study inwhich 20 land use categories were included and the land usecategory of the innermost domain was shown in Figure 1(b)We used the Mellor-Yamada-Janjic PBL scheme [24 25]which was capable of predicting TKE Other physical optionschosen were the Rapid Radiative Transfer Model (RRTM)long-wave scheme [26] the Dudhia shortwave scheme [27]the WRF Single-Moment (WSM) 3-class simple ice scheme[28] Kain-Fritsch (new eta) scheme [29] and the Noah land-surface scheme [30] with a single-layer UCM (Urban CanopyModel) [31 32] The first 16 hours of the simulations wereused as spin-up and WRF output interval was set to 1 hourThe coupling method of Miao et al [18 20] is used to couple

Advances in Meteorology 3

48∘N

46∘N

44∘N

42∘N

40∘N

38∘N

36∘N

116∘E 120

∘E 124∘E 128

∘E

(a)

42∘N

41∘50998400N

41∘40998400N

41∘30998400N

41∘20998400N

123∘10

998400E

123∘20

998400E

123∘30

998400E

123∘40

998400E

123∘50

998400E

Other

Water

Forest

Grassland

Cropland

Urban

(b)

Figure 1 Nested computational domains and the land use category of the innermost domain in the WRF model simulation (a) nestedcomputational domains in the WRF model simulation (b) the land use category of the innermost domain of the WRF model Crosses showthe location of the meteorological observatories

Table 1 Run-time domain configurations and physics options usedin the WRF simulation

Run-time domain configurations andphysics options

Summer-Run From 0800 LST 12 August to 0200 LST 14August 2012

Winter-Run From 0800 LST 15 February to 0200 LST17 February 2012

Domain dimensions 40 times 40 56 times 46 and 51 times 51Grid size 375 75 and 15 kmLand use dataset MODISMicrophysics scheme WSM-3

Radiation scheme RRTM long-wave and Dudhia short-wavescheme

Cumulus scheme Kain-Fritsch (new eta) schemePBL scheme MYJLand surface scheme Noah with single-layer UCM

WRF and OpenFOAM The validations of OpenFOAM canbe found at the study of Miao et al [18 20]

32 CFD Simulation Setup The CFD model simulationdomain covers a part of Northeastern University Chinalocated at the center of Shenyang A Google Earth image andthe CFD model domain with horizontal building configura-tion at the surface were shown in Figure 2 The actual build-ings and their different shapes were simplified to cuboidsand the average height of the buildings was 245m with thetallest and lowest building being 81m and 6mThehorizontalgrid interval was 10m and the horizontal grid dimensionwas 86 times 81 In the vertical a nonuniform grid system with

50 levels was employed in which the vertical grid intervalwas 5m up to the 30th level and the grid interval of thetopmost 20 levels was 10mTheWRF data from one grid thatwas nearest to the location of the CFD domain was used toprovide initial and boundary conditions to OpenFOAMThevelocity components and TKE at the inflow condition canbe directly given by WRF simulation while the momentumdiffusion coefficient was indirectly calculated by Grisogonoscheme [33 34] and the TKEdissipation rate is parameterizedby using these two parameters

120576 =119862120583

1198962

]119905

(1)

where 119896 is the TKE 120576 is its dissipation rate ]119905

is the turbulentexchange coefficient and 119862

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is an empirical constant Tosimulate the wind and turbulent fields of different situationthe initial and boundary conditions of velocity componentsand TKE were set by the simulation of WRF of differentmoments (ie 1400 LST and 2200 LST) The zero-gradientboundary conditionwas employed at the outflow boundariesincluding the top boundary The building surface was set asbeing in a no-slip condition and thewall turbulence functionswere employed to the grid points adjacent to the walls [35]

Three point sources located at different places were hypo-thetically set on the ground level in the built-up area whichwere continuously emitted during the simulation periodThelocations of the two point sources are shown in Figure 2(b)labeled by the crosses one was set at the southern side ofbuilding-A whose height was 81m the other one was set inthe center of build-up area The emission rate of each sourcewas 10 ppm sminus1 and the time step was set to 1 s A seriesof sensitivity studies have been performed resulting in thatthe concentration pattern was stable when the number ofintegral steps reached 5000 and thus the total number of the

4 Advances in Meteorology

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Figure 3 The observed sea level pressure field at (a) 0800 LST 16th of February 2012 and (b) 0800 LST 13th of August 2012

integrate steps was set to 7000 for all the dispersion numericalexperiments

4 Results and Discussions

In this section the two series numerical experiments of theWRF-CFD coupled model on winter and summer would bepresented

41 Simulation Results in Winter

411 Simulation of WRF Winter Experiment Figure 3(a)showed the observed sea level pressure field at 0800 LST 16February 2012 At this time the observed sea level pressurefield exhibited a high pressure system over the Mongoliaregion and a low pressure system over the sea of OkhotskShenyang was located in the uniform pressure field in front ofMongolia high circulation without obvious synoptic system

Severe air pollution often happens in this situation overShenyang area [36]

The measurements from 17 meteorological observatories(Figure 1(b)) located in Shenyang area were used to examinethe accuracy of theWRFmodel Figure 4 showed the diurnalvariations of average observed and WRF-simulated 2-mtemperature and 10-m speed Both the observation and simu-lation are the mean value of the 17 stations or correspondinggrids It is noted that the observed temperature was higherthan simulated one during the winter which was the heatingseason of Shenyang area (Figure 7(a)) This difference mayowe to the underestimation of the anthropogenic heat inWRF As noted in earlier studies the anthropogenic heat haslarger impact on surface air temperature in winter than insummer [37] Despite this deficiency the diurnal temperaturecycle was replicated well by WRF model The accuracy ofwind speed simulation was lower than temperature thesimulated wind speed was higher than observed one This

Advances in Meteorology 5

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is a general tendency by the model to overestimate windspeed found in many earlier studies [38ndash40] A new methodto parameterize the effects that the unresolved topographyexerts over the surface circulations has been implementedin WRFv341+ to correct the high wind speed bias [40] Inaddition the large anthropogenic heat in winter may alsocontribute to the difference between simulated and observedwind speed

Figure 5 exhibited the 10-m wind vector fields and 2-mtemperature fields of the innermost WRF domain on 16thof February 2012 During the studied period the northwestwind dominated the Shenyang area and the wind becameweaker when the ground temperature gets higher Further-more we found that the wind speed in the urban areaof Shenyang was lower than the suburb areas which wasparticularly obvious at 1000 LST and 1400 LST At 2200 LSTthe wind in the southeast off the city turned to the west

Temperature stratification and boundary layer height aretwo important meteorological factors related to pollutantdispersion process Temperature stratification affects verticaldispersion of air pollutant in atmospheric boundary layerand low-level inversion which trapped humidity and pollu-tant is a key factor affecting regional air qualityThe boundarylayer height determines the volume of air which can be usedto dilute pollutants The WRF-simulated potential tempera-ture profile and height-time section of potential temperatureat the grid cell that was nearest to the location of the CFDdomain in WRF were given in Figure 6 The MYJ schemedetermines the PBL height using the TKE profile Since the

TKE is largest within the PBL MYJ defines the top of thePBL to be the height where the TKE decreases to a prescribedlow value [41] which leads to unreliable results during winternight Instead the diurnal variation of boundary layer heightcalculated using the 15-theta-increase method was shown inFigure 6 The 15-theta-increase method defines PBL heightsas the level at which the potential temperature first exceedsthe minimum potential temperature within the boundarylayer by 15 K [42 43] The weak inversion can be seen at0400 LST and the surface layer began to turn into the mixedlayer at 0800 LST at 2000 LST the inversion was formedagain because of the cooling of surface (Figure 6(a)) As wasshown in Figure 6(e) we can clearly see that the inversionwas formed at around 1700 LST and lasted the whole nightFurthermore the boundary layer height (mixed layer height)of the periods in which the inversion existed was lowerthan any other time of the day (Figure 6(c)) which was notgood for the vertical diffusion of pollutant released from theground

412 Simulation of CFDExperiments inWinter According tothe analysis of WRF simulation results two CFD numericalexperiments with different atmospheric boundary conditions(unstable and stable) at differentmoments were set up that is1400 LST and 2200 LST At 1400 LST an unstable mixed layerwas fully developed and reached the highest boundary layerheight (about 18 km) of the winter simulation period andthis unstable boundary structure was good for the verticalmixing process of the pollutant On the contrary a typical

6 Advances in Meteorology

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Figure 5The 10-m wind vector fields and 2-m temperature fields of Shenyang on 16th of February 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

Advances in Meteorology 7

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8 Advances in Meteorology

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Figure 7 Simulated concentration (ppm) and wind vector fields at 1400 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

stable nocturnal boundary layer was established at 2200 LSTwith a lower boundary layer height (about 300 m)

Figure 7 exhibited the simulated concentration (ppm)and wind vector fields for two heights at 1400 LST on 16th ofFebruary At this moment the ambient wind direction givenby the WRF model was northwest and the speed was about35m sminus1 both at 119911 = 25m and 119911 = 225m At 119911 = 25mwind vectors within the buildings were quite different fromthe free wind vectors on the boundary regions under theinfluences of the buildings It was particularly obvious in thesouthern part of the build-up regions where the distributionof the buildings was denser than the other areas When theairflow passed through the building-A two lee side vortexeswere established a strong one was on the southern lee sideof the building-A and the other weak one was on the eastAnd wind speed around the edge of building-A was fastest inthe build-up area Since the building distribution was sparser

at the height of 225m the wind field there was strongerand simpler The two vortexes still existed on the lee sideof building-A Besides that at the height of 225m most ofwind vectors within the building followed the ambient winddirection

At 119911 = 25m when the point source was located at P1driven by the vortex on the lee side of building-A a pollutantplume with concentrations higher than 5 ppm extended asan ellipse-pattern and most of the pollutants were dispersedtoward the southeast (Figure 7(a)) The point source P2 waslocated at a more open area thus the pollutant concentrationwas high only at the southeast of the source due to theblock effect of the building there (Figure 7(b)) Similar to thewind vector fields the concentration field at 119911 = 225m wassimpler than that of lower level most of the pollutants weretransported by the ambient wind direction

Advances in Meteorology 9

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Figure 8 Simulated concentration (ppm) and wind vector fields at 2200 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

At 2200 LST a typical nocturnal stable layer was formednear the surface (Figure 6(e)) which may inhibit the dis-persion process of pollutants Although the ambient windspeed of 2200 LST was higher than that of 1400 LST thepollution could be more serious at 2200 LST with the samepoint source For example in the P1 point source experimentthe polluted area with concentration higher than 01 ppmwassmaller at night (Figures 8(a) and 8(c)) which reflected thatthe diffusion ability was weaker at that moment and morepollutants were trapped in the vortex on the leeward side ofbuilding-A

For the P2 point source experiment as the wind speedincreased the shape of pollution plume was changed a littleand at the height of 25m more pollutants were transportedalong the channel formed by the buildings located on thenorth of P2 Unlike P1 placing on the leeward side building

the P2 point source was set up in a more open area the pollu-tion of P2 was dominated by the convection process ratherthan the turbulent diffusion process Therefore comparingto the daytime unstable situation as wind speed increasedthe convection of the pollutants strengthened and then thepollution was relaxed a little at night (Figures 8(b) and 8(d))

In short it was found that buildings may alter the flowand concentration fields significantly The position of thepoint source had significant influences on the concentrationpattern Comparing the flow and dispersion pattern at twomoments it was found that the convection and turbulentdiffusion were the two important processes to determinethe pollution serious level Within the nocturnal stableatmospheric boundary structure although the ambient windspeed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

10 Advances in Meteorology

42 Simulation Results in Summer

421 Simulation of WRF Summer Experiment Figure 3(b)showed the observed sea level pressure field at 0800 LST 13August 2012 Similar to the winter case the Shenyang areawas under the control of this high pressure system with weaksynoptic system

Figures 4(c) and 4(d) exhibited the diurnal variationsof the observed and simulated 2-m temperature and 10-mwind speed to examine the WRF output The simulatedtemperature was a little lower than observed one at nightand the temperature during the daytime was simulated wellDespite the fact that the simulated wind speed was slightlyhigher the diurnal variation of the wind speed was simulatedwell On the whole the simulation result in summer wasbetter than that in winter

The 10-m wind vector fields and 2-m temperature fieldsof the innermost WRF domain on 16th of February 2012were shown in Figure 9 At 0200 LST the main directionof the wind was northeast while the wind turned to northat 0600 LST The wind speed increased as the land surfacewas heated by the sun It was noted that at 1800 LST thewind direction within the built-up areas of Shenyang wasdifferent from that in the suburb area the wind in the built-up areas was northwestern while the wind in the suburb areawas northern At 2200 LST the wind turned to north in thesimulation region We can also obviously find the urban heatisland effect in Shenyang at 0200 LST 1800 LST and 2200 LSTthe 2-m temperature over the built-up area was significantlyhigher than that of the suburb area

The potential temperature profile height-time section ofthe potential temperature profile and time series of boundarylayer height simulated by WRF were given in Figure 6 Thesurface-based inversion formed at 0400 LST and the intensityof inversion below the height of 500m was 23 K per 100mheight which was stronger than the inversion that happenedin winter at the same time and the depth of the inversionlayer was also thicker than that of winter (Figures 6(a) and6(b)) At 0800 LST since the ground was warmed by thesunlight a thin mixed layer was generated near ground andthe temperature inversion was detached from the ground atthe height of 250m After 0800 LST the low-level inversionlayer disappeared gradually at 1200 LST a mixed layer wasformed in the lower atmosphere from ground to the heightof 700m (Figure 6(b)) In the afternoon the mixed layerextended well to 15 km height (Figure 6(d)) favoring thevertical dilution of pollutant At night the ground was cooledby the nocturnal radiation causing the generation of theinversion stable layer near the ground Comparing to thenocturnal stable layer of the winter case the boundary layerheight of the summer experiment was lower from 0000 LSTto 0600 LST because of the calm ambient wind background(Figures 6(c) and 6(d))

422 Simulation of CFD Experiments in Summer Similarto the winter CFD numerical experiments two experi-ments with different atmospheric boundary structures weredesigned at 1400 LST (unstable case) and 2200 LST (stablecase)

Figure 10 illustrated the simulated concentration (ppm)and wind vector fields at different height at 1400 LST on 13thof August when the ambient wind direction was north Itwas noted that two counterclockwise vortices formed behindbuilding-A which was a typical double-eddy circulationreported by Hunter et al [44] and Zhang et al [45] Compar-ing to the wind vector field at 119911 = 25m the wind vector fieldof 225mwasmuch simpler and the north flowwas dominantin most of the region

At the lower level the distributions of pollutant concen-tration were consistent with the flow patternWhen the pointsourcewas located at P1 or P2 the pollutantswere transportedand trapped in the circulations of the two vortexes behindbuilding-A

Comparing the concentration fields of point sourcesP1 and P2 at two heights it was interesting to find thatthe concentration within the red rectangle in Figure 10 washigher at the height of 225m than the lower level (25mheight) The phenomenon can be explained by the windfields at different height At the height of 25m since redrectangle region was surrounded by buildings where thewind fields were detached from the ambient boundary windand were dominant by the east wind therefore the pollutantreleased from the northern P1 and P2 point sources cannotbe transported to this region directly In the contrary at theheight of 225m the red rectangle regionwas dominant by thenorth wind therefore the pollutant can be easily transportedthere

At 2200 LST when the south ambient wind blew a quitedifferent flow pattern was presented within the built-up area(Figure 11) compared to that of 1400 LST A strong divergencezone can be found in the south of building-A at the heightof 25m indicated by the red dashed rectangle in Figure 11When the airflowblew from the south a typical step-up notchwas formed by building-A (81m) and building-B (24m) asthe vertical wind field presented in Figure 12 the south inletwind was blocked by the taller building (building-A) anddescended along the windward wall of building-A and thendiverged near the ground

At the lower level the wind field around the point sources(P1 and P2) was totally rearranged by the effects of thebuildings around At the height of 225m since the sparserbuilding distribution the wind field was more close to theambient wind Therefore the wind fields of the height of25m and 225m were quite different as well as the pollutantdistributions At 119911 = 25m most of the pollutant releasedfrom P1 and P2 source was transported to south by thedivergence zone formed on the south side building-A

In these two cases it was found that the change of theambient wind direction can significantly affect the flow fieldsand pollutant distributions within the building cluster

5 Discussion and Conclusions

This study examined urban airflow and dispersion patternof pollutant released from hypothetical sources in North-eastern University of Shenyang China by using a WRF-CFD coupled model Two WRF numerical experiments

Advances in Meteorology 11

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Figure 9 The 10-m wind vector fields and 2-m temperature fields of Shenyang on 13th of August 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

12 Advances in Meteorology

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Figure 10 Simulated concentration (ppm) and wind vector fields at 1400 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

(Summer-Run and Winter-Run) were performed to studythe typical features of the atmospheric boundary layer struc-tures of different season Then the coupled WRF-CFD wasused to study how the atmospheric boundary structureambient wind and source position affect the wind fieldand pollutant distribution within the built-up areas It wasfound that the pollutant dispersion pattern and the pollutiondegree dispersion were complicated in the presence of realbuilding clusters and under varying atmospheric bound-ary structures ambient wind and locations of pollutionsources

From this preliminary numerical study it was found thatthe atmospheric boundary structure played a crucial role onthe pollution within the building cluster which determinedthe potential turbulent diffusion ability of the atmosphericsurface layer For example within a nocturnal stable atmo-spheric boundary condition although the ambient wind

speed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

The change of the ambient wind direction can signifi-cantly affect the dispersion pattern of pollutants which was amore sensitive factor than the ambient wind speedThereforewhen a building cluster was designed it was important toconsider the frequency of the ambient wind direction there

Under a given atmospheric state the location of thepollution source would dramatically determine the pollutionpatterns within the built-up areasWhen the pollutant sourcewas set up on the leeward side of the building the pollutantdispersion pattern was dominated by turbulent diffusion pro-cess which was affected by atmospheric boundary structureswhile the convection process dominated when the pollutantsource was set up in a more open area Besides that thedistribution of pollutant concentrationwas driven by the flowpattern

Advances in Meteorology 13

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)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

B

(b)

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

A

(c)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

(d)

Figure 11 Simulated concentration (ppm) and wind vector fields at 2200 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

A

B

90

60

30

0

Z(m

)

Y (m)6005004003002001000

Reference vector3

Figure 12 The vertical plane of the wind vector field across 119883 =325m

Finally it should be noted that the wind fields anddispersion patterns within the building clusters were com-plicated which cannot be obtained from the ambient wind

TheWRF-CFD numerical evaluation can be used as a reliablemethod to understand the complicated flow and dispersionwithin the built-up areas

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is supported by the China Meteorological Admin-istration Special Public Welfare Research Fund under Grantno GYHY201106033 and the National Natural Science Foun-dation of China under Grant no 41175004

14 Advances in Meteorology

References

[1] H R Olesen R Berkowicz M Ketzel and P Loslashfstroslashm ldquoVal-idation of OML AERMODPRIME and MISKAM using theThompson wind-tunnel dataset for simple stack-building con-figurationsrdquo Boundary-LayerMeteorology vol 131 no 1 pp 73ndash83 2009

[2] R S Thompson ldquoBuilding amplification factors for sourcesnear buildings a wind-tunnel studyrdquo Atmospheric EnvironmentPart A General Topics vol 27 no 15 pp 2313ndash2325 1993

[3] A F Stein and B M Toselli ldquoStreet level air pollution in Cor-doba City ArgentinardquoAtmospheric Environment vol 30 no 20pp 3491ndash3495 1996

[4] RWMacDonald R F Griffiths and S C Cheah ldquoField exper-iments of dispersion through regular arrays of cubic structuresrdquoAtmospheric Environment vol 31 no 6 pp 783ndash795 1997

[5] R W Macdonald R F Griffiths and D J Hall ldquoA comparisonof results from scaled field and wind tunnel modelling ofdispersion in arrays of obstaclesrdquoAtmospheric Environment vol32 no 22 pp 3845ndash3862 1998

[6] M Pavageau andM Schatzmann ldquoWind tunnel measurementsof concentration fluctuations in an urban street canyonrdquo Atmo-spheric Environment vol 33 no 24-25 pp 3961ndash3971 1999

[7] P Kastner-Klein and E J Plate ldquoWind-tunnel study of concen-tration fields in street canyonsrdquo Atmospheric Environment vol33 no 24-25 pp 3973ndash3979 1999

[8] I Mavroidis R F Griffiths and D J Hall ldquoField and windtunnel investigations of plume dispersion around single surfaceobstaclesrdquo Atmospheric Environment vol 37 no 21 pp 2903ndash2918 2003

[9] DDelaunay D Lakehal C Barre andC Sacre ldquoNumerical andwind tunnel simulation of gas dispersion around a rectangularbuildingrdquo Journal ofWind Engineeringamp Industrial Aerodynam-ics vol 67-68 pp 721ndash732 1997

[10] I R Cowan I P Castro and A G Robins ldquoNumericalconsiderations for simulations of flow and dispersion aroundbuildingsrdquo Journal of Wind Engineering and Industrial Aerody-namics vol 67-68 pp 535ndash545 1997

[11] J J Baik and J J Kim ldquoOn the escape of pollutants from urbanstreet canyonsrdquo Atmospheric Environment vol 36 no 3 pp527ndash536 2002

[12] K Nazridoust and G Ahmadi ldquoAirflow and pollutant transportin street canyonsrdquo Journal of Wind Engineering and IndustrialAerodynamics vol 94 no 6 pp 491ndash522 2006

[13] Y Tominaga SMurakami andAMochida ldquoCFDprediction ofgaseous diffusion around a cubic model using a dynamic mixedSGSmodel based on composite grid techniquerdquo Journal ofWindEngineering and Industrial Aerodynamics vol 67-68 pp 827ndash841 1997

[14] K Sada and A Sato ldquoNumerical calculation of flow andstack-gas concentration fluctuation around a cubical buildingrdquoAtmospheric Environment vol 36 no 35 pp 5527ndash5534 2002

[15] X-X Li C-H Liu and D Y C Leung ldquoLarge-eddy simulationof flow and pollutant dispersion in high-aspect-ratio urbanstreet canyons with wall modelrdquo Boundary-Layer Meteorologyvol 129 no 2 pp 249ndash268 2008

[16] M Tewari H Kusaka F Chen et al ldquoImpact of couplinga microscale computational fluid dynamics model with amesoscale model on urban scale contaminant transport anddispersionrdquo Atmospheric Research vol 96 no 4 pp 656ndash6642010

[17] Y S Liu S G Miao C L Zhang G X Cui and Z S ZhangldquoStudy on micro-atmospheric environment by coupling largeeddy simulation with mesoscale modelrdquo Journal of Wind Engi-neering amp Industrial Aerodynamics vol 107-108 pp 106ndash1172012

[18] Y Miao S Liu B Chen B Zhang S Wang and S Li ldquoSimu-lating urban flow and dispersion in Beijing by coupling a CFDmodel with theWRFmodelrdquoAdvances in Atmospheric Sciencesvol 30 no 6 pp 1663ndash1678 2013

[19] X Fang W Jiang S Miao et al ldquoThe multi-scale numericalmodeling system for research on the relationship betweenurban planning and meteorological environmentrdquo Advances inAtmospheric Sciences vol 21 no 1 pp 103ndash112 2004

[20] Y C Miao S H Liu H Zheng et al ldquoA multi-scale urbanatmospheric dispersion model for emergency managementrdquoAdvances in Atmospheric Sciences vol 31 no 6 pp 1353ndash13652014

[21] S Miao W Jiang X Wang and W Guo ldquoImpact assessmentof urban meteorology and the atmospheric environment usingurban sub-domain planningrdquoBoundary-LayerMeteorology vol118 no 1 pp 133ndash150 2006

[22] OpenCFD OpenFOAM The Open Source Computational FluidDynamics (CFD) Toolbox 2008 httpwwwopencfdcoukopenfoam

[23] J H Ferziger and M Peric Computational Methods for FluidDynamics Springer Berlin Germany 3rd edition 2001

[24] Z I Janjic ldquoThe step-mountain coordinate physical packagerdquoMonthly Weather Review vol 118 no 7 pp 1429ndash1443 1990

[25] Z I Janjic ldquoThe step-mountain eta coordinate model furtherdevelopments of the convection viscous sublayer and turbu-lence closure schemesrdquoMonthlyWeather Review vol 122 no 5pp 927ndash945 1994

[26] E J Mlawer S J Taubman P D Brown M J Iacono and S AClough ldquoRadiative transfer for inhomogeneous atmospheresRRTM a validated correlated-k model for the longwaverdquoJournal of Geophysical Research Atmospheres vol 102 no 14pp 16663ndash16682 1997

[27] J Dudhia ldquoNumerical study of convection observed dur-ing the winter monsoon experiment using a mesoscale two-dimensionalmodelrdquo Journal of theAtmospheric Sciences vol 46no 20 pp 3077ndash3107 1989

[28] S-Y Hong J Dudhia and S-H Chen ldquoA revised approach toice microphysical processes for the bulk parameterization ofclouds and precipitationrdquoMonthlyWeather Review vol 132 no1 pp 103ndash120 2004

[29] J S Kain ldquoThe Kain Fritsch convective parameterization anupdaterdquo Journal of Applied Meteorology vol 43 no 1 pp 170ndash181 2004

[30] F Chen and J Dudhia ldquoCoupling and advanced land surface-hydrology model with the Penn State-NCAR MM5 modelingsystem Part I model implementation and sensitivityrdquoMonthlyWeather Review vol 129 no 4 pp 569ndash585 2001

[31] H Kusaka H Kondo Y Kikegawa and F Kimura ldquoA simplesingle-layer urban canopy model for atmospheric modelscomparison with multi-layer and slab modelsrdquo Boundary-LayerMeteorology vol 101 no 3 pp 329ndash358 2001

[32] H Kusaka and F Kimura ldquoCoupling a single-layer urbancanopy model with a simple atmospheric model impact onurban heat island simulation for an idealized caserdquo Journal of theMeteorological Society of Japan vol 82 no 1 pp 67ndash80 2004

Advances in Meteorology 15

[33] B Grisogono and J Oerlemans ldquoJustifying the WKB approxi-mation in pure katabatic flowsrdquo Tellus A Dynamic Meteorologyand Oceanography vol 54 no 5 pp 453ndash462 2002

[34] A Jericevic L Kraljevic B Grisogono H Fagerli and Z Vece-naj ldquoParameterization of vertical diffusion and the atmosphericboundary layer height determination in the EMEP modelrdquoAtmospheric Chemistry and Physics vol 10 no 2 pp 341ndash3642010

[35] C Bicheng L ShuhuaM Yucong et al ldquoConstruction and vali-dation of a computational fluid dynamics approach for flow anddispersion modeling in urban areardquo Journal of MeteorologicalResearch vol 27 no 6 pp 923ndash941 2013

[36] C Liqiang and Y Hongbin ldquoSynoptic patterns of regional airpollution in Liaoning Provincerdquo Environmental Pollution ampControl vol 28 no 6 pp 435ndash451 2006 (Chinese)

[37] S A Adachi H KusakaM G Duda et al ldquoImprovement of thesingle-layer UCM in the WRF modelrdquo in Proceedings of the 8thInternational Conference on Urban Climates (ICUC8 rsquo12) 2012

[38] G Roux Y Liu L D Monache et al ldquoVerification of highresolution WRF-RTFDDA surface forecasts over mountainsand plainsrdquo Proceedings of the 10th WRF Usersrsquo Workshop pp20ndash23 2009

[39] S Shimada T Ohsawa S Chikaoka et al ldquoAccuracy of the windspeed profile in the lower PBL as simulated by theWRFmodelrdquoSola vol 7 pp 109ndash112 2011

[40] P A Jimenez and J Dudhia ldquoImproving the representation ofresolved and unresolved topographic effects on surface wind inthe wrf modelrdquo Journal of AppliedMeteorology and Climatologyvol 51 no 2 pp 300ndash316 2012

[41] Z I Janjic ldquoNonsingular implementation of theMellor-Yamadalevel 25 scheme in the NCEP Meso modelrdquo NOAANWSNCEP Office Note 437 2001

[42] X-M Hu J W Nielsen-Gammon and F Zhang ldquoEvaluationof three planetary boundary layer schemes in the WRF modelrdquoJournal of Applied Meteorology and Climatology vol 49 no 9pp 1831ndash1844 2010

[43] J W Nielsen-Gammon C L Powell M J Mahoney et alldquoMultisensor estimation of mixing heights over a coastal cityrdquoJournal of Applied Meteorology and Climatology vol 47 no 1pp 27ndash43 2008

[44] L J Hunter G T Johnson and I D Watson ldquoAn investigationof three-dimensional characteristics of flow regimes withinthe urban canyonrdquo Atmospheric Environment Part B UrbanAtmosphere vol 26 no 4 pp 425ndash432 1992

[45] Y Q Zhang S P Arya and W H Snyder ldquoA comparisonof numerical and physical modeling of stable atmosphericflow and dispersion around a cubical buildingrdquo AtmosphericEnvironment vol 30 no 8 pp 1327ndash1345 1996

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

Advances in Meteorology 3

48∘N

46∘N

44∘N

42∘N

40∘N

38∘N

36∘N

116∘E 120

∘E 124∘E 128

∘E

(a)

42∘N

41∘50998400N

41∘40998400N

41∘30998400N

41∘20998400N

123∘10

998400E

123∘20

998400E

123∘30

998400E

123∘40

998400E

123∘50

998400E

Other

Water

Forest

Grassland

Cropland

Urban

(b)

Figure 1 Nested computational domains and the land use category of the innermost domain in the WRF model simulation (a) nestedcomputational domains in the WRF model simulation (b) the land use category of the innermost domain of the WRF model Crosses showthe location of the meteorological observatories

Table 1 Run-time domain configurations and physics options usedin the WRF simulation

Run-time domain configurations andphysics options

Summer-Run From 0800 LST 12 August to 0200 LST 14August 2012

Winter-Run From 0800 LST 15 February to 0200 LST17 February 2012

Domain dimensions 40 times 40 56 times 46 and 51 times 51Grid size 375 75 and 15 kmLand use dataset MODISMicrophysics scheme WSM-3

Radiation scheme RRTM long-wave and Dudhia short-wavescheme

Cumulus scheme Kain-Fritsch (new eta) schemePBL scheme MYJLand surface scheme Noah with single-layer UCM

WRF and OpenFOAM The validations of OpenFOAM canbe found at the study of Miao et al [18 20]

32 CFD Simulation Setup The CFD model simulationdomain covers a part of Northeastern University Chinalocated at the center of Shenyang A Google Earth image andthe CFD model domain with horizontal building configura-tion at the surface were shown in Figure 2 The actual build-ings and their different shapes were simplified to cuboidsand the average height of the buildings was 245m with thetallest and lowest building being 81m and 6mThehorizontalgrid interval was 10m and the horizontal grid dimensionwas 86 times 81 In the vertical a nonuniform grid system with

50 levels was employed in which the vertical grid intervalwas 5m up to the 30th level and the grid interval of thetopmost 20 levels was 10mTheWRF data from one grid thatwas nearest to the location of the CFD domain was used toprovide initial and boundary conditions to OpenFOAMThevelocity components and TKE at the inflow condition canbe directly given by WRF simulation while the momentumdiffusion coefficient was indirectly calculated by Grisogonoscheme [33 34] and the TKEdissipation rate is parameterizedby using these two parameters

120576 =119862120583

1198962

]119905

(1)

where 119896 is the TKE 120576 is its dissipation rate ]119905

is the turbulentexchange coefficient and 119862

120583

is an empirical constant Tosimulate the wind and turbulent fields of different situationthe initial and boundary conditions of velocity componentsand TKE were set by the simulation of WRF of differentmoments (ie 1400 LST and 2200 LST) The zero-gradientboundary conditionwas employed at the outflow boundariesincluding the top boundary The building surface was set asbeing in a no-slip condition and thewall turbulence functionswere employed to the grid points adjacent to the walls [35]

Three point sources located at different places were hypo-thetically set on the ground level in the built-up area whichwere continuously emitted during the simulation periodThelocations of the two point sources are shown in Figure 2(b)labeled by the crosses one was set at the southern side ofbuilding-A whose height was 81m the other one was set inthe center of build-up area The emission rate of each sourcewas 10 ppm sminus1 and the time step was set to 1 s A seriesof sensitivity studies have been performed resulting in thatthe concentration pattern was stable when the number ofintegral steps reached 5000 and thus the total number of the

4 Advances in Meteorology

(a)

P1

P2

A

600

600

500

500

400

400

300

300

200

200

100

100

Y(m

)

0

0

X (m)

A

(b)

Figure 2 Google Earth image and the horizontal plane of the CFD computation domain (a) Google Earth image of Northeastern University(b) the horizontal plane of the CFD computation domain at 119911 = 25mThe red rectangle in (a) indicates the CFD domain the crosses labeledby P1 and P2 in (b) indicate the locations of point sources

50∘N

45∘N

40∘N

35∘N

30∘N

100∘E 110

∘E 120∘E 130

∘E 140∘E

H1052

1044 1044

1036

1036

1028 10201012

1012

1012

1028

1028

L1013

L984

(a)

L1006L1001

L1002

L1000

H1011

H1014

1008

1008

1008

1000

1008

1008

1004

1008

1004

1004

1004

1004

100∘E 110

∘E 120∘E 130

∘E 140∘E

50∘N

45∘N

40∘N

35∘N

30∘N

(b)

Figure 3 The observed sea level pressure field at (a) 0800 LST 16th of February 2012 and (b) 0800 LST 13th of August 2012

integrate steps was set to 7000 for all the dispersion numericalexperiments

4 Results and Discussions

In this section the two series numerical experiments of theWRF-CFD coupled model on winter and summer would bepresented

41 Simulation Results in Winter

411 Simulation of WRF Winter Experiment Figure 3(a)showed the observed sea level pressure field at 0800 LST 16February 2012 At this time the observed sea level pressurefield exhibited a high pressure system over the Mongoliaregion and a low pressure system over the sea of OkhotskShenyang was located in the uniform pressure field in front ofMongolia high circulation without obvious synoptic system

Severe air pollution often happens in this situation overShenyang area [36]

The measurements from 17 meteorological observatories(Figure 1(b)) located in Shenyang area were used to examinethe accuracy of theWRFmodel Figure 4 showed the diurnalvariations of average observed and WRF-simulated 2-mtemperature and 10-m speed Both the observation and simu-lation are the mean value of the 17 stations or correspondinggrids It is noted that the observed temperature was higherthan simulated one during the winter which was the heatingseason of Shenyang area (Figure 7(a)) This difference mayowe to the underestimation of the anthropogenic heat inWRF As noted in earlier studies the anthropogenic heat haslarger impact on surface air temperature in winter than insummer [37] Despite this deficiency the diurnal temperaturecycle was replicated well by WRF model The accuracy ofwind speed simulation was lower than temperature thesimulated wind speed was higher than observed one This

Advances in Meteorology 5

0200 0600 1000 1400 1800 2200February 16th (hour)

0

minus5

minus10

minus15

minus20Tem

pera

ture

2m

(∘C)

(a)

0200 0600 1000 1400 1800 22000

2

4

6

February 16th (hour)

Win

d sp

eed10

m (m

sminus1)

(b)

0200 0600 1000 1400 1800 2200

SimulationObservation

August 13th (hour)

5101520253035

Tem

pera

ture

2m

(∘C)

(c)

0200 0600 1000 1400 1800 22000

2

4

6

SimulationObservation

August 13th (hour)

Win

d sp

eed10

m (m

sminus1)

(d)

Figure 4 Time series of observed and WRF-simulated results (a c) 2-m temperature (b d) 10-m wind speed (a b) simulation on 16February 2012 (c d) simulation on 13 August 2012 The observation is the mean value of 17 meteorological stations around Shenyang whilethe simulation is the average of the values taken at the grids nearest to the stations

is a general tendency by the model to overestimate windspeed found in many earlier studies [38ndash40] A new methodto parameterize the effects that the unresolved topographyexerts over the surface circulations has been implementedin WRFv341+ to correct the high wind speed bias [40] Inaddition the large anthropogenic heat in winter may alsocontribute to the difference between simulated and observedwind speed

Figure 5 exhibited the 10-m wind vector fields and 2-mtemperature fields of the innermost WRF domain on 16thof February 2012 During the studied period the northwestwind dominated the Shenyang area and the wind becameweaker when the ground temperature gets higher Further-more we found that the wind speed in the urban areaof Shenyang was lower than the suburb areas which wasparticularly obvious at 1000 LST and 1400 LST At 2200 LSTthe wind in the southeast off the city turned to the west

Temperature stratification and boundary layer height aretwo important meteorological factors related to pollutantdispersion process Temperature stratification affects verticaldispersion of air pollutant in atmospheric boundary layerand low-level inversion which trapped humidity and pollu-tant is a key factor affecting regional air qualityThe boundarylayer height determines the volume of air which can be usedto dilute pollutants The WRF-simulated potential tempera-ture profile and height-time section of potential temperatureat the grid cell that was nearest to the location of the CFDdomain in WRF were given in Figure 6 The MYJ schemedetermines the PBL height using the TKE profile Since the

TKE is largest within the PBL MYJ defines the top of thePBL to be the height where the TKE decreases to a prescribedlow value [41] which leads to unreliable results during winternight Instead the diurnal variation of boundary layer heightcalculated using the 15-theta-increase method was shown inFigure 6 The 15-theta-increase method defines PBL heightsas the level at which the potential temperature first exceedsthe minimum potential temperature within the boundarylayer by 15 K [42 43] The weak inversion can be seen at0400 LST and the surface layer began to turn into the mixedlayer at 0800 LST at 2000 LST the inversion was formedagain because of the cooling of surface (Figure 6(a)) As wasshown in Figure 6(e) we can clearly see that the inversionwas formed at around 1700 LST and lasted the whole nightFurthermore the boundary layer height (mixed layer height)of the periods in which the inversion existed was lowerthan any other time of the day (Figure 6(c)) which was notgood for the vertical diffusion of pollutant released from theground

412 Simulation of CFDExperiments inWinter According tothe analysis of WRF simulation results two CFD numericalexperiments with different atmospheric boundary conditions(unstable and stable) at differentmoments were set up that is1400 LST and 2200 LST At 1400 LST an unstable mixed layerwas fully developed and reached the highest boundary layerheight (about 18 km) of the winter simulation period andthis unstable boundary structure was good for the verticalmixing process of the pollutant On the contrary a typical

6 Advances in Meteorology

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(a)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

minus16

minus15

minus14

minus13

minus12

minus11

minus10

minus9

minus86

Reference vector

Tem

pera

ture

2m

(∘C)

(b)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N123

∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(c)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

minus16

minus15

minus14

minus13

minus12

minus11

minus10

minus9

minus8

6

Reference vector

Tem

pera

ture

2m

(∘C)

(d)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(e)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

minus16

minus15

minus14

minus13

minus12

minus11

minus10

minus9

minus86

Reference vectorTe

mpe

ratu

re2

m (∘

C)

(f)

Figure 5The 10-m wind vector fields and 2-m temperature fields of Shenyang on 16th of February 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

Advances in Meteorology 7

08 LST04 LST

2500

2000

1500

1000

500

0

255 258 261 264 267 270 273

Hei

ght (

m)

Potential temperature (K)

20 LST16 LST12 LST

(a)

2500

2000

1500

1000

500

0

Hei

ght (

m)

Potential temperature (K)285 288 291 294 297 300 303 306

08 LST04 LST

20 LST16 LST12 LST

(b)

1600

1400

1200

1000

800

600

400

200

0

0600 1400 2200Time

PBL

heig

ht (m

)

(c)

14000600 2200Time

1600

1400

1200

1000

800

600

400

200

0

PBL

heig

ht (m

)

(d)

400

8001200

20001600

0 4 8 12 16 20

Time (hour)

Hei

ght (

m)

260

262

264

266

268

270

272

Tem

pera

ture

(K)

(e)

400

8001200

20001600

Hei

ght (

m)

288

292

296

300

304

0 4 8 12 16 20

Time (hour)

Tem

pera

ture

(K)

(f)

Figure 6 The simulated boundary layer structure of WRF (a b) potential temperature profile (c d) diurnal variation of boundary layerheight (e f) height-time section of potential temperature (a c e) simulation on 16 February 2012 (b d f) simulation on 13 August 2012

8 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(c)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(d)

Figure 7 Simulated concentration (ppm) and wind vector fields at 1400 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

stable nocturnal boundary layer was established at 2200 LSTwith a lower boundary layer height (about 300 m)

Figure 7 exhibited the simulated concentration (ppm)and wind vector fields for two heights at 1400 LST on 16th ofFebruary At this moment the ambient wind direction givenby the WRF model was northwest and the speed was about35m sminus1 both at 119911 = 25m and 119911 = 225m At 119911 = 25mwind vectors within the buildings were quite different fromthe free wind vectors on the boundary regions under theinfluences of the buildings It was particularly obvious in thesouthern part of the build-up regions where the distributionof the buildings was denser than the other areas When theairflow passed through the building-A two lee side vortexeswere established a strong one was on the southern lee sideof the building-A and the other weak one was on the eastAnd wind speed around the edge of building-A was fastest inthe build-up area Since the building distribution was sparser

at the height of 225m the wind field there was strongerand simpler The two vortexes still existed on the lee sideof building-A Besides that at the height of 225m most ofwind vectors within the building followed the ambient winddirection

At 119911 = 25m when the point source was located at P1driven by the vortex on the lee side of building-A a pollutantplume with concentrations higher than 5 ppm extended asan ellipse-pattern and most of the pollutants were dispersedtoward the southeast (Figure 7(a)) The point source P2 waslocated at a more open area thus the pollutant concentrationwas high only at the southeast of the source due to theblock effect of the building there (Figure 7(b)) Similar to thewind vector fields the concentration field at 119911 = 225m wassimpler than that of lower level most of the pollutants weretransported by the ambient wind direction

Advances in Meteorology 9

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

(c)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(d)

Figure 8 Simulated concentration (ppm) and wind vector fields at 2200 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

At 2200 LST a typical nocturnal stable layer was formednear the surface (Figure 6(e)) which may inhibit the dis-persion process of pollutants Although the ambient windspeed of 2200 LST was higher than that of 1400 LST thepollution could be more serious at 2200 LST with the samepoint source For example in the P1 point source experimentthe polluted area with concentration higher than 01 ppmwassmaller at night (Figures 8(a) and 8(c)) which reflected thatthe diffusion ability was weaker at that moment and morepollutants were trapped in the vortex on the leeward side ofbuilding-A

For the P2 point source experiment as the wind speedincreased the shape of pollution plume was changed a littleand at the height of 25m more pollutants were transportedalong the channel formed by the buildings located on thenorth of P2 Unlike P1 placing on the leeward side building

the P2 point source was set up in a more open area the pollu-tion of P2 was dominated by the convection process ratherthan the turbulent diffusion process Therefore comparingto the daytime unstable situation as wind speed increasedthe convection of the pollutants strengthened and then thepollution was relaxed a little at night (Figures 8(b) and 8(d))

In short it was found that buildings may alter the flowand concentration fields significantly The position of thepoint source had significant influences on the concentrationpattern Comparing the flow and dispersion pattern at twomoments it was found that the convection and turbulentdiffusion were the two important processes to determinethe pollution serious level Within the nocturnal stableatmospheric boundary structure although the ambient windspeed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

10 Advances in Meteorology

42 Simulation Results in Summer

421 Simulation of WRF Summer Experiment Figure 3(b)showed the observed sea level pressure field at 0800 LST 13August 2012 Similar to the winter case the Shenyang areawas under the control of this high pressure system with weaksynoptic system

Figures 4(c) and 4(d) exhibited the diurnal variationsof the observed and simulated 2-m temperature and 10-mwind speed to examine the WRF output The simulatedtemperature was a little lower than observed one at nightand the temperature during the daytime was simulated wellDespite the fact that the simulated wind speed was slightlyhigher the diurnal variation of the wind speed was simulatedwell On the whole the simulation result in summer wasbetter than that in winter

The 10-m wind vector fields and 2-m temperature fieldsof the innermost WRF domain on 16th of February 2012were shown in Figure 9 At 0200 LST the main directionof the wind was northeast while the wind turned to northat 0600 LST The wind speed increased as the land surfacewas heated by the sun It was noted that at 1800 LST thewind direction within the built-up areas of Shenyang wasdifferent from that in the suburb area the wind in the built-up areas was northwestern while the wind in the suburb areawas northern At 2200 LST the wind turned to north in thesimulation region We can also obviously find the urban heatisland effect in Shenyang at 0200 LST 1800 LST and 2200 LSTthe 2-m temperature over the built-up area was significantlyhigher than that of the suburb area

The potential temperature profile height-time section ofthe potential temperature profile and time series of boundarylayer height simulated by WRF were given in Figure 6 Thesurface-based inversion formed at 0400 LST and the intensityof inversion below the height of 500m was 23 K per 100mheight which was stronger than the inversion that happenedin winter at the same time and the depth of the inversionlayer was also thicker than that of winter (Figures 6(a) and6(b)) At 0800 LST since the ground was warmed by thesunlight a thin mixed layer was generated near ground andthe temperature inversion was detached from the ground atthe height of 250m After 0800 LST the low-level inversionlayer disappeared gradually at 1200 LST a mixed layer wasformed in the lower atmosphere from ground to the heightof 700m (Figure 6(b)) In the afternoon the mixed layerextended well to 15 km height (Figure 6(d)) favoring thevertical dilution of pollutant At night the ground was cooledby the nocturnal radiation causing the generation of theinversion stable layer near the ground Comparing to thenocturnal stable layer of the winter case the boundary layerheight of the summer experiment was lower from 0000 LSTto 0600 LST because of the calm ambient wind background(Figures 6(c) and 6(d))

422 Simulation of CFD Experiments in Summer Similarto the winter CFD numerical experiments two experi-ments with different atmospheric boundary structures weredesigned at 1400 LST (unstable case) and 2200 LST (stablecase)

Figure 10 illustrated the simulated concentration (ppm)and wind vector fields at different height at 1400 LST on 13thof August when the ambient wind direction was north Itwas noted that two counterclockwise vortices formed behindbuilding-A which was a typical double-eddy circulationreported by Hunter et al [44] and Zhang et al [45] Compar-ing to the wind vector field at 119911 = 25m the wind vector fieldof 225mwasmuch simpler and the north flowwas dominantin most of the region

At the lower level the distributions of pollutant concen-tration were consistent with the flow patternWhen the pointsourcewas located at P1 or P2 the pollutantswere transportedand trapped in the circulations of the two vortexes behindbuilding-A

Comparing the concentration fields of point sourcesP1 and P2 at two heights it was interesting to find thatthe concentration within the red rectangle in Figure 10 washigher at the height of 225m than the lower level (25mheight) The phenomenon can be explained by the windfields at different height At the height of 25m since redrectangle region was surrounded by buildings where thewind fields were detached from the ambient boundary windand were dominant by the east wind therefore the pollutantreleased from the northern P1 and P2 point sources cannotbe transported to this region directly In the contrary at theheight of 225m the red rectangle regionwas dominant by thenorth wind therefore the pollutant can be easily transportedthere

At 2200 LST when the south ambient wind blew a quitedifferent flow pattern was presented within the built-up area(Figure 11) compared to that of 1400 LST A strong divergencezone can be found in the south of building-A at the heightof 25m indicated by the red dashed rectangle in Figure 11When the airflowblew from the south a typical step-up notchwas formed by building-A (81m) and building-B (24m) asthe vertical wind field presented in Figure 12 the south inletwind was blocked by the taller building (building-A) anddescended along the windward wall of building-A and thendiverged near the ground

At the lower level the wind field around the point sources(P1 and P2) was totally rearranged by the effects of thebuildings around At the height of 225m since the sparserbuilding distribution the wind field was more close to theambient wind Therefore the wind fields of the height of25m and 225m were quite different as well as the pollutantdistributions At 119911 = 25m most of the pollutant releasedfrom P1 and P2 source was transported to south by thedivergence zone formed on the south side building-A

In these two cases it was found that the change of theambient wind direction can significantly affect the flow fieldsand pollutant distributions within the building cluster

5 Discussion and Conclusions

This study examined urban airflow and dispersion patternof pollutant released from hypothetical sources in North-eastern University of Shenyang China by using a WRF-CFD coupled model Two WRF numerical experiments

Advances in Meteorology 11

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(a)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(b)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(c)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(d)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(e)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(f)

Figure 9 The 10-m wind vector fields and 2-m temperature fields of Shenyang on 13th of August 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

12 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

(c)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

01

05

1

25

5

10

20

35

50

(d)

Figure 10 Simulated concentration (ppm) and wind vector fields at 1400 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

(Summer-Run and Winter-Run) were performed to studythe typical features of the atmospheric boundary layer struc-tures of different season Then the coupled WRF-CFD wasused to study how the atmospheric boundary structureambient wind and source position affect the wind fieldand pollutant distribution within the built-up areas It wasfound that the pollutant dispersion pattern and the pollutiondegree dispersion were complicated in the presence of realbuilding clusters and under varying atmospheric bound-ary structures ambient wind and locations of pollutionsources

From this preliminary numerical study it was found thatthe atmospheric boundary structure played a crucial role onthe pollution within the building cluster which determinedthe potential turbulent diffusion ability of the atmosphericsurface layer For example within a nocturnal stable atmo-spheric boundary condition although the ambient wind

speed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

The change of the ambient wind direction can signifi-cantly affect the dispersion pattern of pollutants which was amore sensitive factor than the ambient wind speedThereforewhen a building cluster was designed it was important toconsider the frequency of the ambient wind direction there

Under a given atmospheric state the location of thepollution source would dramatically determine the pollutionpatterns within the built-up areasWhen the pollutant sourcewas set up on the leeward side of the building the pollutantdispersion pattern was dominated by turbulent diffusion pro-cess which was affected by atmospheric boundary structureswhile the convection process dominated when the pollutantsource was set up in a more open area Besides that thedistribution of pollutant concentrationwas driven by the flowpattern

Advances in Meteorology 13

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

A

B

3

Reference vector

A

B

(a)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

B

(b)

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

A

(c)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

(d)

Figure 11 Simulated concentration (ppm) and wind vector fields at 2200 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

A

B

90

60

30

0

Z(m

)

Y (m)6005004003002001000

Reference vector3

Figure 12 The vertical plane of the wind vector field across 119883 =325m

Finally it should be noted that the wind fields anddispersion patterns within the building clusters were com-plicated which cannot be obtained from the ambient wind

TheWRF-CFD numerical evaluation can be used as a reliablemethod to understand the complicated flow and dispersionwithin the built-up areas

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is supported by the China Meteorological Admin-istration Special Public Welfare Research Fund under Grantno GYHY201106033 and the National Natural Science Foun-dation of China under Grant no 41175004

14 Advances in Meteorology

References

[1] H R Olesen R Berkowicz M Ketzel and P Loslashfstroslashm ldquoVal-idation of OML AERMODPRIME and MISKAM using theThompson wind-tunnel dataset for simple stack-building con-figurationsrdquo Boundary-LayerMeteorology vol 131 no 1 pp 73ndash83 2009

[2] R S Thompson ldquoBuilding amplification factors for sourcesnear buildings a wind-tunnel studyrdquo Atmospheric EnvironmentPart A General Topics vol 27 no 15 pp 2313ndash2325 1993

[3] A F Stein and B M Toselli ldquoStreet level air pollution in Cor-doba City ArgentinardquoAtmospheric Environment vol 30 no 20pp 3491ndash3495 1996

[4] RWMacDonald R F Griffiths and S C Cheah ldquoField exper-iments of dispersion through regular arrays of cubic structuresrdquoAtmospheric Environment vol 31 no 6 pp 783ndash795 1997

[5] R W Macdonald R F Griffiths and D J Hall ldquoA comparisonof results from scaled field and wind tunnel modelling ofdispersion in arrays of obstaclesrdquoAtmospheric Environment vol32 no 22 pp 3845ndash3862 1998

[6] M Pavageau andM Schatzmann ldquoWind tunnel measurementsof concentration fluctuations in an urban street canyonrdquo Atmo-spheric Environment vol 33 no 24-25 pp 3961ndash3971 1999

[7] P Kastner-Klein and E J Plate ldquoWind-tunnel study of concen-tration fields in street canyonsrdquo Atmospheric Environment vol33 no 24-25 pp 3973ndash3979 1999

[8] I Mavroidis R F Griffiths and D J Hall ldquoField and windtunnel investigations of plume dispersion around single surfaceobstaclesrdquo Atmospheric Environment vol 37 no 21 pp 2903ndash2918 2003

[9] DDelaunay D Lakehal C Barre andC Sacre ldquoNumerical andwind tunnel simulation of gas dispersion around a rectangularbuildingrdquo Journal ofWind Engineeringamp Industrial Aerodynam-ics vol 67-68 pp 721ndash732 1997

[10] I R Cowan I P Castro and A G Robins ldquoNumericalconsiderations for simulations of flow and dispersion aroundbuildingsrdquo Journal of Wind Engineering and Industrial Aerody-namics vol 67-68 pp 535ndash545 1997

[11] J J Baik and J J Kim ldquoOn the escape of pollutants from urbanstreet canyonsrdquo Atmospheric Environment vol 36 no 3 pp527ndash536 2002

[12] K Nazridoust and G Ahmadi ldquoAirflow and pollutant transportin street canyonsrdquo Journal of Wind Engineering and IndustrialAerodynamics vol 94 no 6 pp 491ndash522 2006

[13] Y Tominaga SMurakami andAMochida ldquoCFDprediction ofgaseous diffusion around a cubic model using a dynamic mixedSGSmodel based on composite grid techniquerdquo Journal ofWindEngineering and Industrial Aerodynamics vol 67-68 pp 827ndash841 1997

[14] K Sada and A Sato ldquoNumerical calculation of flow andstack-gas concentration fluctuation around a cubical buildingrdquoAtmospheric Environment vol 36 no 35 pp 5527ndash5534 2002

[15] X-X Li C-H Liu and D Y C Leung ldquoLarge-eddy simulationof flow and pollutant dispersion in high-aspect-ratio urbanstreet canyons with wall modelrdquo Boundary-Layer Meteorologyvol 129 no 2 pp 249ndash268 2008

[16] M Tewari H Kusaka F Chen et al ldquoImpact of couplinga microscale computational fluid dynamics model with amesoscale model on urban scale contaminant transport anddispersionrdquo Atmospheric Research vol 96 no 4 pp 656ndash6642010

[17] Y S Liu S G Miao C L Zhang G X Cui and Z S ZhangldquoStudy on micro-atmospheric environment by coupling largeeddy simulation with mesoscale modelrdquo Journal of Wind Engi-neering amp Industrial Aerodynamics vol 107-108 pp 106ndash1172012

[18] Y Miao S Liu B Chen B Zhang S Wang and S Li ldquoSimu-lating urban flow and dispersion in Beijing by coupling a CFDmodel with theWRFmodelrdquoAdvances in Atmospheric Sciencesvol 30 no 6 pp 1663ndash1678 2013

[19] X Fang W Jiang S Miao et al ldquoThe multi-scale numericalmodeling system for research on the relationship betweenurban planning and meteorological environmentrdquo Advances inAtmospheric Sciences vol 21 no 1 pp 103ndash112 2004

[20] Y C Miao S H Liu H Zheng et al ldquoA multi-scale urbanatmospheric dispersion model for emergency managementrdquoAdvances in Atmospheric Sciences vol 31 no 6 pp 1353ndash13652014

[21] S Miao W Jiang X Wang and W Guo ldquoImpact assessmentof urban meteorology and the atmospheric environment usingurban sub-domain planningrdquoBoundary-LayerMeteorology vol118 no 1 pp 133ndash150 2006

[22] OpenCFD OpenFOAM The Open Source Computational FluidDynamics (CFD) Toolbox 2008 httpwwwopencfdcoukopenfoam

[23] J H Ferziger and M Peric Computational Methods for FluidDynamics Springer Berlin Germany 3rd edition 2001

[24] Z I Janjic ldquoThe step-mountain coordinate physical packagerdquoMonthly Weather Review vol 118 no 7 pp 1429ndash1443 1990

[25] Z I Janjic ldquoThe step-mountain eta coordinate model furtherdevelopments of the convection viscous sublayer and turbu-lence closure schemesrdquoMonthlyWeather Review vol 122 no 5pp 927ndash945 1994

[26] E J Mlawer S J Taubman P D Brown M J Iacono and S AClough ldquoRadiative transfer for inhomogeneous atmospheresRRTM a validated correlated-k model for the longwaverdquoJournal of Geophysical Research Atmospheres vol 102 no 14pp 16663ndash16682 1997

[27] J Dudhia ldquoNumerical study of convection observed dur-ing the winter monsoon experiment using a mesoscale two-dimensionalmodelrdquo Journal of theAtmospheric Sciences vol 46no 20 pp 3077ndash3107 1989

[28] S-Y Hong J Dudhia and S-H Chen ldquoA revised approach toice microphysical processes for the bulk parameterization ofclouds and precipitationrdquoMonthlyWeather Review vol 132 no1 pp 103ndash120 2004

[29] J S Kain ldquoThe Kain Fritsch convective parameterization anupdaterdquo Journal of Applied Meteorology vol 43 no 1 pp 170ndash181 2004

[30] F Chen and J Dudhia ldquoCoupling and advanced land surface-hydrology model with the Penn State-NCAR MM5 modelingsystem Part I model implementation and sensitivityrdquoMonthlyWeather Review vol 129 no 4 pp 569ndash585 2001

[31] H Kusaka H Kondo Y Kikegawa and F Kimura ldquoA simplesingle-layer urban canopy model for atmospheric modelscomparison with multi-layer and slab modelsrdquo Boundary-LayerMeteorology vol 101 no 3 pp 329ndash358 2001

[32] H Kusaka and F Kimura ldquoCoupling a single-layer urbancanopy model with a simple atmospheric model impact onurban heat island simulation for an idealized caserdquo Journal of theMeteorological Society of Japan vol 82 no 1 pp 67ndash80 2004

Advances in Meteorology 15

[33] B Grisogono and J Oerlemans ldquoJustifying the WKB approxi-mation in pure katabatic flowsrdquo Tellus A Dynamic Meteorologyand Oceanography vol 54 no 5 pp 453ndash462 2002

[34] A Jericevic L Kraljevic B Grisogono H Fagerli and Z Vece-naj ldquoParameterization of vertical diffusion and the atmosphericboundary layer height determination in the EMEP modelrdquoAtmospheric Chemistry and Physics vol 10 no 2 pp 341ndash3642010

[35] C Bicheng L ShuhuaM Yucong et al ldquoConstruction and vali-dation of a computational fluid dynamics approach for flow anddispersion modeling in urban areardquo Journal of MeteorologicalResearch vol 27 no 6 pp 923ndash941 2013

[36] C Liqiang and Y Hongbin ldquoSynoptic patterns of regional airpollution in Liaoning Provincerdquo Environmental Pollution ampControl vol 28 no 6 pp 435ndash451 2006 (Chinese)

[37] S A Adachi H KusakaM G Duda et al ldquoImprovement of thesingle-layer UCM in the WRF modelrdquo in Proceedings of the 8thInternational Conference on Urban Climates (ICUC8 rsquo12) 2012

[38] G Roux Y Liu L D Monache et al ldquoVerification of highresolution WRF-RTFDDA surface forecasts over mountainsand plainsrdquo Proceedings of the 10th WRF Usersrsquo Workshop pp20ndash23 2009

[39] S Shimada T Ohsawa S Chikaoka et al ldquoAccuracy of the windspeed profile in the lower PBL as simulated by theWRFmodelrdquoSola vol 7 pp 109ndash112 2011

[40] P A Jimenez and J Dudhia ldquoImproving the representation ofresolved and unresolved topographic effects on surface wind inthe wrf modelrdquo Journal of AppliedMeteorology and Climatologyvol 51 no 2 pp 300ndash316 2012

[41] Z I Janjic ldquoNonsingular implementation of theMellor-Yamadalevel 25 scheme in the NCEP Meso modelrdquo NOAANWSNCEP Office Note 437 2001

[42] X-M Hu J W Nielsen-Gammon and F Zhang ldquoEvaluationof three planetary boundary layer schemes in the WRF modelrdquoJournal of Applied Meteorology and Climatology vol 49 no 9pp 1831ndash1844 2010

[43] J W Nielsen-Gammon C L Powell M J Mahoney et alldquoMultisensor estimation of mixing heights over a coastal cityrdquoJournal of Applied Meteorology and Climatology vol 47 no 1pp 27ndash43 2008

[44] L J Hunter G T Johnson and I D Watson ldquoAn investigationof three-dimensional characteristics of flow regimes withinthe urban canyonrdquo Atmospheric Environment Part B UrbanAtmosphere vol 26 no 4 pp 425ndash432 1992

[45] Y Q Zhang S P Arya and W H Snyder ldquoA comparisonof numerical and physical modeling of stable atmosphericflow and dispersion around a cubical buildingrdquo AtmosphericEnvironment vol 30 no 8 pp 1327ndash1345 1996

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

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Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

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MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

4 Advances in Meteorology

(a)

P1

P2

A

600

600

500

500

400

400

300

300

200

200

100

100

Y(m

)

0

0

X (m)

A

(b)

Figure 2 Google Earth image and the horizontal plane of the CFD computation domain (a) Google Earth image of Northeastern University(b) the horizontal plane of the CFD computation domain at 119911 = 25mThe red rectangle in (a) indicates the CFD domain the crosses labeledby P1 and P2 in (b) indicate the locations of point sources

50∘N

45∘N

40∘N

35∘N

30∘N

100∘E 110

∘E 120∘E 130

∘E 140∘E

H1052

1044 1044

1036

1036

1028 10201012

1012

1012

1028

1028

L1013

L984

(a)

L1006L1001

L1002

L1000

H1011

H1014

1008

1008

1008

1000

1008

1008

1004

1008

1004

1004

1004

1004

100∘E 110

∘E 120∘E 130

∘E 140∘E

50∘N

45∘N

40∘N

35∘N

30∘N

(b)

Figure 3 The observed sea level pressure field at (a) 0800 LST 16th of February 2012 and (b) 0800 LST 13th of August 2012

integrate steps was set to 7000 for all the dispersion numericalexperiments

4 Results and Discussions

In this section the two series numerical experiments of theWRF-CFD coupled model on winter and summer would bepresented

41 Simulation Results in Winter

411 Simulation of WRF Winter Experiment Figure 3(a)showed the observed sea level pressure field at 0800 LST 16February 2012 At this time the observed sea level pressurefield exhibited a high pressure system over the Mongoliaregion and a low pressure system over the sea of OkhotskShenyang was located in the uniform pressure field in front ofMongolia high circulation without obvious synoptic system

Severe air pollution often happens in this situation overShenyang area [36]

The measurements from 17 meteorological observatories(Figure 1(b)) located in Shenyang area were used to examinethe accuracy of theWRFmodel Figure 4 showed the diurnalvariations of average observed and WRF-simulated 2-mtemperature and 10-m speed Both the observation and simu-lation are the mean value of the 17 stations or correspondinggrids It is noted that the observed temperature was higherthan simulated one during the winter which was the heatingseason of Shenyang area (Figure 7(a)) This difference mayowe to the underestimation of the anthropogenic heat inWRF As noted in earlier studies the anthropogenic heat haslarger impact on surface air temperature in winter than insummer [37] Despite this deficiency the diurnal temperaturecycle was replicated well by WRF model The accuracy ofwind speed simulation was lower than temperature thesimulated wind speed was higher than observed one This

Advances in Meteorology 5

0200 0600 1000 1400 1800 2200February 16th (hour)

0

minus5

minus10

minus15

minus20Tem

pera

ture

2m

(∘C)

(a)

0200 0600 1000 1400 1800 22000

2

4

6

February 16th (hour)

Win

d sp

eed10

m (m

sminus1)

(b)

0200 0600 1000 1400 1800 2200

SimulationObservation

August 13th (hour)

5101520253035

Tem

pera

ture

2m

(∘C)

(c)

0200 0600 1000 1400 1800 22000

2

4

6

SimulationObservation

August 13th (hour)

Win

d sp

eed10

m (m

sminus1)

(d)

Figure 4 Time series of observed and WRF-simulated results (a c) 2-m temperature (b d) 10-m wind speed (a b) simulation on 16February 2012 (c d) simulation on 13 August 2012 The observation is the mean value of 17 meteorological stations around Shenyang whilethe simulation is the average of the values taken at the grids nearest to the stations

is a general tendency by the model to overestimate windspeed found in many earlier studies [38ndash40] A new methodto parameterize the effects that the unresolved topographyexerts over the surface circulations has been implementedin WRFv341+ to correct the high wind speed bias [40] Inaddition the large anthropogenic heat in winter may alsocontribute to the difference between simulated and observedwind speed

Figure 5 exhibited the 10-m wind vector fields and 2-mtemperature fields of the innermost WRF domain on 16thof February 2012 During the studied period the northwestwind dominated the Shenyang area and the wind becameweaker when the ground temperature gets higher Further-more we found that the wind speed in the urban areaof Shenyang was lower than the suburb areas which wasparticularly obvious at 1000 LST and 1400 LST At 2200 LSTthe wind in the southeast off the city turned to the west

Temperature stratification and boundary layer height aretwo important meteorological factors related to pollutantdispersion process Temperature stratification affects verticaldispersion of air pollutant in atmospheric boundary layerand low-level inversion which trapped humidity and pollu-tant is a key factor affecting regional air qualityThe boundarylayer height determines the volume of air which can be usedto dilute pollutants The WRF-simulated potential tempera-ture profile and height-time section of potential temperatureat the grid cell that was nearest to the location of the CFDdomain in WRF were given in Figure 6 The MYJ schemedetermines the PBL height using the TKE profile Since the

TKE is largest within the PBL MYJ defines the top of thePBL to be the height where the TKE decreases to a prescribedlow value [41] which leads to unreliable results during winternight Instead the diurnal variation of boundary layer heightcalculated using the 15-theta-increase method was shown inFigure 6 The 15-theta-increase method defines PBL heightsas the level at which the potential temperature first exceedsthe minimum potential temperature within the boundarylayer by 15 K [42 43] The weak inversion can be seen at0400 LST and the surface layer began to turn into the mixedlayer at 0800 LST at 2000 LST the inversion was formedagain because of the cooling of surface (Figure 6(a)) As wasshown in Figure 6(e) we can clearly see that the inversionwas formed at around 1700 LST and lasted the whole nightFurthermore the boundary layer height (mixed layer height)of the periods in which the inversion existed was lowerthan any other time of the day (Figure 6(c)) which was notgood for the vertical diffusion of pollutant released from theground

412 Simulation of CFDExperiments inWinter According tothe analysis of WRF simulation results two CFD numericalexperiments with different atmospheric boundary conditions(unstable and stable) at differentmoments were set up that is1400 LST and 2200 LST At 1400 LST an unstable mixed layerwas fully developed and reached the highest boundary layerheight (about 18 km) of the winter simulation period andthis unstable boundary structure was good for the verticalmixing process of the pollutant On the contrary a typical

6 Advances in Meteorology

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(a)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

minus16

minus15

minus14

minus13

minus12

minus11

minus10

minus9

minus86

Reference vector

Tem

pera

ture

2m

(∘C)

(b)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N123

∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(c)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

minus16

minus15

minus14

minus13

minus12

minus11

minus10

minus9

minus8

6

Reference vector

Tem

pera

ture

2m

(∘C)

(d)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(e)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

minus16

minus15

minus14

minus13

minus12

minus11

minus10

minus9

minus86

Reference vectorTe

mpe

ratu

re2

m (∘

C)

(f)

Figure 5The 10-m wind vector fields and 2-m temperature fields of Shenyang on 16th of February 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

Advances in Meteorology 7

08 LST04 LST

2500

2000

1500

1000

500

0

255 258 261 264 267 270 273

Hei

ght (

m)

Potential temperature (K)

20 LST16 LST12 LST

(a)

2500

2000

1500

1000

500

0

Hei

ght (

m)

Potential temperature (K)285 288 291 294 297 300 303 306

08 LST04 LST

20 LST16 LST12 LST

(b)

1600

1400

1200

1000

800

600

400

200

0

0600 1400 2200Time

PBL

heig

ht (m

)

(c)

14000600 2200Time

1600

1400

1200

1000

800

600

400

200

0

PBL

heig

ht (m

)

(d)

400

8001200

20001600

0 4 8 12 16 20

Time (hour)

Hei

ght (

m)

260

262

264

266

268

270

272

Tem

pera

ture

(K)

(e)

400

8001200

20001600

Hei

ght (

m)

288

292

296

300

304

0 4 8 12 16 20

Time (hour)

Tem

pera

ture

(K)

(f)

Figure 6 The simulated boundary layer structure of WRF (a b) potential temperature profile (c d) diurnal variation of boundary layerheight (e f) height-time section of potential temperature (a c e) simulation on 16 February 2012 (b d f) simulation on 13 August 2012

8 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(c)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(d)

Figure 7 Simulated concentration (ppm) and wind vector fields at 1400 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

stable nocturnal boundary layer was established at 2200 LSTwith a lower boundary layer height (about 300 m)

Figure 7 exhibited the simulated concentration (ppm)and wind vector fields for two heights at 1400 LST on 16th ofFebruary At this moment the ambient wind direction givenby the WRF model was northwest and the speed was about35m sminus1 both at 119911 = 25m and 119911 = 225m At 119911 = 25mwind vectors within the buildings were quite different fromthe free wind vectors on the boundary regions under theinfluences of the buildings It was particularly obvious in thesouthern part of the build-up regions where the distributionof the buildings was denser than the other areas When theairflow passed through the building-A two lee side vortexeswere established a strong one was on the southern lee sideof the building-A and the other weak one was on the eastAnd wind speed around the edge of building-A was fastest inthe build-up area Since the building distribution was sparser

at the height of 225m the wind field there was strongerand simpler The two vortexes still existed on the lee sideof building-A Besides that at the height of 225m most ofwind vectors within the building followed the ambient winddirection

At 119911 = 25m when the point source was located at P1driven by the vortex on the lee side of building-A a pollutantplume with concentrations higher than 5 ppm extended asan ellipse-pattern and most of the pollutants were dispersedtoward the southeast (Figure 7(a)) The point source P2 waslocated at a more open area thus the pollutant concentrationwas high only at the southeast of the source due to theblock effect of the building there (Figure 7(b)) Similar to thewind vector fields the concentration field at 119911 = 225m wassimpler than that of lower level most of the pollutants weretransported by the ambient wind direction

Advances in Meteorology 9

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

(c)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(d)

Figure 8 Simulated concentration (ppm) and wind vector fields at 2200 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

At 2200 LST a typical nocturnal stable layer was formednear the surface (Figure 6(e)) which may inhibit the dis-persion process of pollutants Although the ambient windspeed of 2200 LST was higher than that of 1400 LST thepollution could be more serious at 2200 LST with the samepoint source For example in the P1 point source experimentthe polluted area with concentration higher than 01 ppmwassmaller at night (Figures 8(a) and 8(c)) which reflected thatthe diffusion ability was weaker at that moment and morepollutants were trapped in the vortex on the leeward side ofbuilding-A

For the P2 point source experiment as the wind speedincreased the shape of pollution plume was changed a littleand at the height of 25m more pollutants were transportedalong the channel formed by the buildings located on thenorth of P2 Unlike P1 placing on the leeward side building

the P2 point source was set up in a more open area the pollu-tion of P2 was dominated by the convection process ratherthan the turbulent diffusion process Therefore comparingto the daytime unstable situation as wind speed increasedthe convection of the pollutants strengthened and then thepollution was relaxed a little at night (Figures 8(b) and 8(d))

In short it was found that buildings may alter the flowand concentration fields significantly The position of thepoint source had significant influences on the concentrationpattern Comparing the flow and dispersion pattern at twomoments it was found that the convection and turbulentdiffusion were the two important processes to determinethe pollution serious level Within the nocturnal stableatmospheric boundary structure although the ambient windspeed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

10 Advances in Meteorology

42 Simulation Results in Summer

421 Simulation of WRF Summer Experiment Figure 3(b)showed the observed sea level pressure field at 0800 LST 13August 2012 Similar to the winter case the Shenyang areawas under the control of this high pressure system with weaksynoptic system

Figures 4(c) and 4(d) exhibited the diurnal variationsof the observed and simulated 2-m temperature and 10-mwind speed to examine the WRF output The simulatedtemperature was a little lower than observed one at nightand the temperature during the daytime was simulated wellDespite the fact that the simulated wind speed was slightlyhigher the diurnal variation of the wind speed was simulatedwell On the whole the simulation result in summer wasbetter than that in winter

The 10-m wind vector fields and 2-m temperature fieldsof the innermost WRF domain on 16th of February 2012were shown in Figure 9 At 0200 LST the main directionof the wind was northeast while the wind turned to northat 0600 LST The wind speed increased as the land surfacewas heated by the sun It was noted that at 1800 LST thewind direction within the built-up areas of Shenyang wasdifferent from that in the suburb area the wind in the built-up areas was northwestern while the wind in the suburb areawas northern At 2200 LST the wind turned to north in thesimulation region We can also obviously find the urban heatisland effect in Shenyang at 0200 LST 1800 LST and 2200 LSTthe 2-m temperature over the built-up area was significantlyhigher than that of the suburb area

The potential temperature profile height-time section ofthe potential temperature profile and time series of boundarylayer height simulated by WRF were given in Figure 6 Thesurface-based inversion formed at 0400 LST and the intensityof inversion below the height of 500m was 23 K per 100mheight which was stronger than the inversion that happenedin winter at the same time and the depth of the inversionlayer was also thicker than that of winter (Figures 6(a) and6(b)) At 0800 LST since the ground was warmed by thesunlight a thin mixed layer was generated near ground andthe temperature inversion was detached from the ground atthe height of 250m After 0800 LST the low-level inversionlayer disappeared gradually at 1200 LST a mixed layer wasformed in the lower atmosphere from ground to the heightof 700m (Figure 6(b)) In the afternoon the mixed layerextended well to 15 km height (Figure 6(d)) favoring thevertical dilution of pollutant At night the ground was cooledby the nocturnal radiation causing the generation of theinversion stable layer near the ground Comparing to thenocturnal stable layer of the winter case the boundary layerheight of the summer experiment was lower from 0000 LSTto 0600 LST because of the calm ambient wind background(Figures 6(c) and 6(d))

422 Simulation of CFD Experiments in Summer Similarto the winter CFD numerical experiments two experi-ments with different atmospheric boundary structures weredesigned at 1400 LST (unstable case) and 2200 LST (stablecase)

Figure 10 illustrated the simulated concentration (ppm)and wind vector fields at different height at 1400 LST on 13thof August when the ambient wind direction was north Itwas noted that two counterclockwise vortices formed behindbuilding-A which was a typical double-eddy circulationreported by Hunter et al [44] and Zhang et al [45] Compar-ing to the wind vector field at 119911 = 25m the wind vector fieldof 225mwasmuch simpler and the north flowwas dominantin most of the region

At the lower level the distributions of pollutant concen-tration were consistent with the flow patternWhen the pointsourcewas located at P1 or P2 the pollutantswere transportedand trapped in the circulations of the two vortexes behindbuilding-A

Comparing the concentration fields of point sourcesP1 and P2 at two heights it was interesting to find thatthe concentration within the red rectangle in Figure 10 washigher at the height of 225m than the lower level (25mheight) The phenomenon can be explained by the windfields at different height At the height of 25m since redrectangle region was surrounded by buildings where thewind fields were detached from the ambient boundary windand were dominant by the east wind therefore the pollutantreleased from the northern P1 and P2 point sources cannotbe transported to this region directly In the contrary at theheight of 225m the red rectangle regionwas dominant by thenorth wind therefore the pollutant can be easily transportedthere

At 2200 LST when the south ambient wind blew a quitedifferent flow pattern was presented within the built-up area(Figure 11) compared to that of 1400 LST A strong divergencezone can be found in the south of building-A at the heightof 25m indicated by the red dashed rectangle in Figure 11When the airflowblew from the south a typical step-up notchwas formed by building-A (81m) and building-B (24m) asthe vertical wind field presented in Figure 12 the south inletwind was blocked by the taller building (building-A) anddescended along the windward wall of building-A and thendiverged near the ground

At the lower level the wind field around the point sources(P1 and P2) was totally rearranged by the effects of thebuildings around At the height of 225m since the sparserbuilding distribution the wind field was more close to theambient wind Therefore the wind fields of the height of25m and 225m were quite different as well as the pollutantdistributions At 119911 = 25m most of the pollutant releasedfrom P1 and P2 source was transported to south by thedivergence zone formed on the south side building-A

In these two cases it was found that the change of theambient wind direction can significantly affect the flow fieldsand pollutant distributions within the building cluster

5 Discussion and Conclusions

This study examined urban airflow and dispersion patternof pollutant released from hypothetical sources in North-eastern University of Shenyang China by using a WRF-CFD coupled model Two WRF numerical experiments

Advances in Meteorology 11

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(a)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(b)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(c)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(d)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(e)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(f)

Figure 9 The 10-m wind vector fields and 2-m temperature fields of Shenyang on 13th of August 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

12 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

(c)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

01

05

1

25

5

10

20

35

50

(d)

Figure 10 Simulated concentration (ppm) and wind vector fields at 1400 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

(Summer-Run and Winter-Run) were performed to studythe typical features of the atmospheric boundary layer struc-tures of different season Then the coupled WRF-CFD wasused to study how the atmospheric boundary structureambient wind and source position affect the wind fieldand pollutant distribution within the built-up areas It wasfound that the pollutant dispersion pattern and the pollutiondegree dispersion were complicated in the presence of realbuilding clusters and under varying atmospheric bound-ary structures ambient wind and locations of pollutionsources

From this preliminary numerical study it was found thatthe atmospheric boundary structure played a crucial role onthe pollution within the building cluster which determinedthe potential turbulent diffusion ability of the atmosphericsurface layer For example within a nocturnal stable atmo-spheric boundary condition although the ambient wind

speed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

The change of the ambient wind direction can signifi-cantly affect the dispersion pattern of pollutants which was amore sensitive factor than the ambient wind speedThereforewhen a building cluster was designed it was important toconsider the frequency of the ambient wind direction there

Under a given atmospheric state the location of thepollution source would dramatically determine the pollutionpatterns within the built-up areasWhen the pollutant sourcewas set up on the leeward side of the building the pollutantdispersion pattern was dominated by turbulent diffusion pro-cess which was affected by atmospheric boundary structureswhile the convection process dominated when the pollutantsource was set up in a more open area Besides that thedistribution of pollutant concentrationwas driven by the flowpattern

Advances in Meteorology 13

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

A

B

3

Reference vector

A

B

(a)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

B

(b)

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

A

(c)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

(d)

Figure 11 Simulated concentration (ppm) and wind vector fields at 2200 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

A

B

90

60

30

0

Z(m

)

Y (m)6005004003002001000

Reference vector3

Figure 12 The vertical plane of the wind vector field across 119883 =325m

Finally it should be noted that the wind fields anddispersion patterns within the building clusters were com-plicated which cannot be obtained from the ambient wind

TheWRF-CFD numerical evaluation can be used as a reliablemethod to understand the complicated flow and dispersionwithin the built-up areas

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is supported by the China Meteorological Admin-istration Special Public Welfare Research Fund under Grantno GYHY201106033 and the National Natural Science Foun-dation of China under Grant no 41175004

14 Advances in Meteorology

References

[1] H R Olesen R Berkowicz M Ketzel and P Loslashfstroslashm ldquoVal-idation of OML AERMODPRIME and MISKAM using theThompson wind-tunnel dataset for simple stack-building con-figurationsrdquo Boundary-LayerMeteorology vol 131 no 1 pp 73ndash83 2009

[2] R S Thompson ldquoBuilding amplification factors for sourcesnear buildings a wind-tunnel studyrdquo Atmospheric EnvironmentPart A General Topics vol 27 no 15 pp 2313ndash2325 1993

[3] A F Stein and B M Toselli ldquoStreet level air pollution in Cor-doba City ArgentinardquoAtmospheric Environment vol 30 no 20pp 3491ndash3495 1996

[4] RWMacDonald R F Griffiths and S C Cheah ldquoField exper-iments of dispersion through regular arrays of cubic structuresrdquoAtmospheric Environment vol 31 no 6 pp 783ndash795 1997

[5] R W Macdonald R F Griffiths and D J Hall ldquoA comparisonof results from scaled field and wind tunnel modelling ofdispersion in arrays of obstaclesrdquoAtmospheric Environment vol32 no 22 pp 3845ndash3862 1998

[6] M Pavageau andM Schatzmann ldquoWind tunnel measurementsof concentration fluctuations in an urban street canyonrdquo Atmo-spheric Environment vol 33 no 24-25 pp 3961ndash3971 1999

[7] P Kastner-Klein and E J Plate ldquoWind-tunnel study of concen-tration fields in street canyonsrdquo Atmospheric Environment vol33 no 24-25 pp 3973ndash3979 1999

[8] I Mavroidis R F Griffiths and D J Hall ldquoField and windtunnel investigations of plume dispersion around single surfaceobstaclesrdquo Atmospheric Environment vol 37 no 21 pp 2903ndash2918 2003

[9] DDelaunay D Lakehal C Barre andC Sacre ldquoNumerical andwind tunnel simulation of gas dispersion around a rectangularbuildingrdquo Journal ofWind Engineeringamp Industrial Aerodynam-ics vol 67-68 pp 721ndash732 1997

[10] I R Cowan I P Castro and A G Robins ldquoNumericalconsiderations for simulations of flow and dispersion aroundbuildingsrdquo Journal of Wind Engineering and Industrial Aerody-namics vol 67-68 pp 535ndash545 1997

[11] J J Baik and J J Kim ldquoOn the escape of pollutants from urbanstreet canyonsrdquo Atmospheric Environment vol 36 no 3 pp527ndash536 2002

[12] K Nazridoust and G Ahmadi ldquoAirflow and pollutant transportin street canyonsrdquo Journal of Wind Engineering and IndustrialAerodynamics vol 94 no 6 pp 491ndash522 2006

[13] Y Tominaga SMurakami andAMochida ldquoCFDprediction ofgaseous diffusion around a cubic model using a dynamic mixedSGSmodel based on composite grid techniquerdquo Journal ofWindEngineering and Industrial Aerodynamics vol 67-68 pp 827ndash841 1997

[14] K Sada and A Sato ldquoNumerical calculation of flow andstack-gas concentration fluctuation around a cubical buildingrdquoAtmospheric Environment vol 36 no 35 pp 5527ndash5534 2002

[15] X-X Li C-H Liu and D Y C Leung ldquoLarge-eddy simulationof flow and pollutant dispersion in high-aspect-ratio urbanstreet canyons with wall modelrdquo Boundary-Layer Meteorologyvol 129 no 2 pp 249ndash268 2008

[16] M Tewari H Kusaka F Chen et al ldquoImpact of couplinga microscale computational fluid dynamics model with amesoscale model on urban scale contaminant transport anddispersionrdquo Atmospheric Research vol 96 no 4 pp 656ndash6642010

[17] Y S Liu S G Miao C L Zhang G X Cui and Z S ZhangldquoStudy on micro-atmospheric environment by coupling largeeddy simulation with mesoscale modelrdquo Journal of Wind Engi-neering amp Industrial Aerodynamics vol 107-108 pp 106ndash1172012

[18] Y Miao S Liu B Chen B Zhang S Wang and S Li ldquoSimu-lating urban flow and dispersion in Beijing by coupling a CFDmodel with theWRFmodelrdquoAdvances in Atmospheric Sciencesvol 30 no 6 pp 1663ndash1678 2013

[19] X Fang W Jiang S Miao et al ldquoThe multi-scale numericalmodeling system for research on the relationship betweenurban planning and meteorological environmentrdquo Advances inAtmospheric Sciences vol 21 no 1 pp 103ndash112 2004

[20] Y C Miao S H Liu H Zheng et al ldquoA multi-scale urbanatmospheric dispersion model for emergency managementrdquoAdvances in Atmospheric Sciences vol 31 no 6 pp 1353ndash13652014

[21] S Miao W Jiang X Wang and W Guo ldquoImpact assessmentof urban meteorology and the atmospheric environment usingurban sub-domain planningrdquoBoundary-LayerMeteorology vol118 no 1 pp 133ndash150 2006

[22] OpenCFD OpenFOAM The Open Source Computational FluidDynamics (CFD) Toolbox 2008 httpwwwopencfdcoukopenfoam

[23] J H Ferziger and M Peric Computational Methods for FluidDynamics Springer Berlin Germany 3rd edition 2001

[24] Z I Janjic ldquoThe step-mountain coordinate physical packagerdquoMonthly Weather Review vol 118 no 7 pp 1429ndash1443 1990

[25] Z I Janjic ldquoThe step-mountain eta coordinate model furtherdevelopments of the convection viscous sublayer and turbu-lence closure schemesrdquoMonthlyWeather Review vol 122 no 5pp 927ndash945 1994

[26] E J Mlawer S J Taubman P D Brown M J Iacono and S AClough ldquoRadiative transfer for inhomogeneous atmospheresRRTM a validated correlated-k model for the longwaverdquoJournal of Geophysical Research Atmospheres vol 102 no 14pp 16663ndash16682 1997

[27] J Dudhia ldquoNumerical study of convection observed dur-ing the winter monsoon experiment using a mesoscale two-dimensionalmodelrdquo Journal of theAtmospheric Sciences vol 46no 20 pp 3077ndash3107 1989

[28] S-Y Hong J Dudhia and S-H Chen ldquoA revised approach toice microphysical processes for the bulk parameterization ofclouds and precipitationrdquoMonthlyWeather Review vol 132 no1 pp 103ndash120 2004

[29] J S Kain ldquoThe Kain Fritsch convective parameterization anupdaterdquo Journal of Applied Meteorology vol 43 no 1 pp 170ndash181 2004

[30] F Chen and J Dudhia ldquoCoupling and advanced land surface-hydrology model with the Penn State-NCAR MM5 modelingsystem Part I model implementation and sensitivityrdquoMonthlyWeather Review vol 129 no 4 pp 569ndash585 2001

[31] H Kusaka H Kondo Y Kikegawa and F Kimura ldquoA simplesingle-layer urban canopy model for atmospheric modelscomparison with multi-layer and slab modelsrdquo Boundary-LayerMeteorology vol 101 no 3 pp 329ndash358 2001

[32] H Kusaka and F Kimura ldquoCoupling a single-layer urbancanopy model with a simple atmospheric model impact onurban heat island simulation for an idealized caserdquo Journal of theMeteorological Society of Japan vol 82 no 1 pp 67ndash80 2004

Advances in Meteorology 15

[33] B Grisogono and J Oerlemans ldquoJustifying the WKB approxi-mation in pure katabatic flowsrdquo Tellus A Dynamic Meteorologyand Oceanography vol 54 no 5 pp 453ndash462 2002

[34] A Jericevic L Kraljevic B Grisogono H Fagerli and Z Vece-naj ldquoParameterization of vertical diffusion and the atmosphericboundary layer height determination in the EMEP modelrdquoAtmospheric Chemistry and Physics vol 10 no 2 pp 341ndash3642010

[35] C Bicheng L ShuhuaM Yucong et al ldquoConstruction and vali-dation of a computational fluid dynamics approach for flow anddispersion modeling in urban areardquo Journal of MeteorologicalResearch vol 27 no 6 pp 923ndash941 2013

[36] C Liqiang and Y Hongbin ldquoSynoptic patterns of regional airpollution in Liaoning Provincerdquo Environmental Pollution ampControl vol 28 no 6 pp 435ndash451 2006 (Chinese)

[37] S A Adachi H KusakaM G Duda et al ldquoImprovement of thesingle-layer UCM in the WRF modelrdquo in Proceedings of the 8thInternational Conference on Urban Climates (ICUC8 rsquo12) 2012

[38] G Roux Y Liu L D Monache et al ldquoVerification of highresolution WRF-RTFDDA surface forecasts over mountainsand plainsrdquo Proceedings of the 10th WRF Usersrsquo Workshop pp20ndash23 2009

[39] S Shimada T Ohsawa S Chikaoka et al ldquoAccuracy of the windspeed profile in the lower PBL as simulated by theWRFmodelrdquoSola vol 7 pp 109ndash112 2011

[40] P A Jimenez and J Dudhia ldquoImproving the representation ofresolved and unresolved topographic effects on surface wind inthe wrf modelrdquo Journal of AppliedMeteorology and Climatologyvol 51 no 2 pp 300ndash316 2012

[41] Z I Janjic ldquoNonsingular implementation of theMellor-Yamadalevel 25 scheme in the NCEP Meso modelrdquo NOAANWSNCEP Office Note 437 2001

[42] X-M Hu J W Nielsen-Gammon and F Zhang ldquoEvaluationof three planetary boundary layer schemes in the WRF modelrdquoJournal of Applied Meteorology and Climatology vol 49 no 9pp 1831ndash1844 2010

[43] J W Nielsen-Gammon C L Powell M J Mahoney et alldquoMultisensor estimation of mixing heights over a coastal cityrdquoJournal of Applied Meteorology and Climatology vol 47 no 1pp 27ndash43 2008

[44] L J Hunter G T Johnson and I D Watson ldquoAn investigationof three-dimensional characteristics of flow regimes withinthe urban canyonrdquo Atmospheric Environment Part B UrbanAtmosphere vol 26 no 4 pp 425ndash432 1992

[45] Y Q Zhang S P Arya and W H Snyder ldquoA comparisonof numerical and physical modeling of stable atmosphericflow and dispersion around a cubical buildingrdquo AtmosphericEnvironment vol 30 no 8 pp 1327ndash1345 1996

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

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Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

Advances in Meteorology 5

0200 0600 1000 1400 1800 2200February 16th (hour)

0

minus5

minus10

minus15

minus20Tem

pera

ture

2m

(∘C)

(a)

0200 0600 1000 1400 1800 22000

2

4

6

February 16th (hour)

Win

d sp

eed10

m (m

sminus1)

(b)

0200 0600 1000 1400 1800 2200

SimulationObservation

August 13th (hour)

5101520253035

Tem

pera

ture

2m

(∘C)

(c)

0200 0600 1000 1400 1800 22000

2

4

6

SimulationObservation

August 13th (hour)

Win

d sp

eed10

m (m

sminus1)

(d)

Figure 4 Time series of observed and WRF-simulated results (a c) 2-m temperature (b d) 10-m wind speed (a b) simulation on 16February 2012 (c d) simulation on 13 August 2012 The observation is the mean value of 17 meteorological stations around Shenyang whilethe simulation is the average of the values taken at the grids nearest to the stations

is a general tendency by the model to overestimate windspeed found in many earlier studies [38ndash40] A new methodto parameterize the effects that the unresolved topographyexerts over the surface circulations has been implementedin WRFv341+ to correct the high wind speed bias [40] Inaddition the large anthropogenic heat in winter may alsocontribute to the difference between simulated and observedwind speed

Figure 5 exhibited the 10-m wind vector fields and 2-mtemperature fields of the innermost WRF domain on 16thof February 2012 During the studied period the northwestwind dominated the Shenyang area and the wind becameweaker when the ground temperature gets higher Further-more we found that the wind speed in the urban areaof Shenyang was lower than the suburb areas which wasparticularly obvious at 1000 LST and 1400 LST At 2200 LSTthe wind in the southeast off the city turned to the west

Temperature stratification and boundary layer height aretwo important meteorological factors related to pollutantdispersion process Temperature stratification affects verticaldispersion of air pollutant in atmospheric boundary layerand low-level inversion which trapped humidity and pollu-tant is a key factor affecting regional air qualityThe boundarylayer height determines the volume of air which can be usedto dilute pollutants The WRF-simulated potential tempera-ture profile and height-time section of potential temperatureat the grid cell that was nearest to the location of the CFDdomain in WRF were given in Figure 6 The MYJ schemedetermines the PBL height using the TKE profile Since the

TKE is largest within the PBL MYJ defines the top of thePBL to be the height where the TKE decreases to a prescribedlow value [41] which leads to unreliable results during winternight Instead the diurnal variation of boundary layer heightcalculated using the 15-theta-increase method was shown inFigure 6 The 15-theta-increase method defines PBL heightsas the level at which the potential temperature first exceedsthe minimum potential temperature within the boundarylayer by 15 K [42 43] The weak inversion can be seen at0400 LST and the surface layer began to turn into the mixedlayer at 0800 LST at 2000 LST the inversion was formedagain because of the cooling of surface (Figure 6(a)) As wasshown in Figure 6(e) we can clearly see that the inversionwas formed at around 1700 LST and lasted the whole nightFurthermore the boundary layer height (mixed layer height)of the periods in which the inversion existed was lowerthan any other time of the day (Figure 6(c)) which was notgood for the vertical diffusion of pollutant released from theground

412 Simulation of CFDExperiments inWinter According tothe analysis of WRF simulation results two CFD numericalexperiments with different atmospheric boundary conditions(unstable and stable) at differentmoments were set up that is1400 LST and 2200 LST At 1400 LST an unstable mixed layerwas fully developed and reached the highest boundary layerheight (about 18 km) of the winter simulation period andthis unstable boundary structure was good for the verticalmixing process of the pollutant On the contrary a typical

6 Advances in Meteorology

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(a)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

minus16

minus15

minus14

minus13

minus12

minus11

minus10

minus9

minus86

Reference vector

Tem

pera

ture

2m

(∘C)

(b)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N123

∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(c)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

minus16

minus15

minus14

minus13

minus12

minus11

minus10

minus9

minus8

6

Reference vector

Tem

pera

ture

2m

(∘C)

(d)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(e)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

minus16

minus15

minus14

minus13

minus12

minus11

minus10

minus9

minus86

Reference vectorTe

mpe

ratu

re2

m (∘

C)

(f)

Figure 5The 10-m wind vector fields and 2-m temperature fields of Shenyang on 16th of February 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

Advances in Meteorology 7

08 LST04 LST

2500

2000

1500

1000

500

0

255 258 261 264 267 270 273

Hei

ght (

m)

Potential temperature (K)

20 LST16 LST12 LST

(a)

2500

2000

1500

1000

500

0

Hei

ght (

m)

Potential temperature (K)285 288 291 294 297 300 303 306

08 LST04 LST

20 LST16 LST12 LST

(b)

1600

1400

1200

1000

800

600

400

200

0

0600 1400 2200Time

PBL

heig

ht (m

)

(c)

14000600 2200Time

1600

1400

1200

1000

800

600

400

200

0

PBL

heig

ht (m

)

(d)

400

8001200

20001600

0 4 8 12 16 20

Time (hour)

Hei

ght (

m)

260

262

264

266

268

270

272

Tem

pera

ture

(K)

(e)

400

8001200

20001600

Hei

ght (

m)

288

292

296

300

304

0 4 8 12 16 20

Time (hour)

Tem

pera

ture

(K)

(f)

Figure 6 The simulated boundary layer structure of WRF (a b) potential temperature profile (c d) diurnal variation of boundary layerheight (e f) height-time section of potential temperature (a c e) simulation on 16 February 2012 (b d f) simulation on 13 August 2012

8 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(c)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(d)

Figure 7 Simulated concentration (ppm) and wind vector fields at 1400 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

stable nocturnal boundary layer was established at 2200 LSTwith a lower boundary layer height (about 300 m)

Figure 7 exhibited the simulated concentration (ppm)and wind vector fields for two heights at 1400 LST on 16th ofFebruary At this moment the ambient wind direction givenby the WRF model was northwest and the speed was about35m sminus1 both at 119911 = 25m and 119911 = 225m At 119911 = 25mwind vectors within the buildings were quite different fromthe free wind vectors on the boundary regions under theinfluences of the buildings It was particularly obvious in thesouthern part of the build-up regions where the distributionof the buildings was denser than the other areas When theairflow passed through the building-A two lee side vortexeswere established a strong one was on the southern lee sideof the building-A and the other weak one was on the eastAnd wind speed around the edge of building-A was fastest inthe build-up area Since the building distribution was sparser

at the height of 225m the wind field there was strongerand simpler The two vortexes still existed on the lee sideof building-A Besides that at the height of 225m most ofwind vectors within the building followed the ambient winddirection

At 119911 = 25m when the point source was located at P1driven by the vortex on the lee side of building-A a pollutantplume with concentrations higher than 5 ppm extended asan ellipse-pattern and most of the pollutants were dispersedtoward the southeast (Figure 7(a)) The point source P2 waslocated at a more open area thus the pollutant concentrationwas high only at the southeast of the source due to theblock effect of the building there (Figure 7(b)) Similar to thewind vector fields the concentration field at 119911 = 225m wassimpler than that of lower level most of the pollutants weretransported by the ambient wind direction

Advances in Meteorology 9

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

(c)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(d)

Figure 8 Simulated concentration (ppm) and wind vector fields at 2200 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

At 2200 LST a typical nocturnal stable layer was formednear the surface (Figure 6(e)) which may inhibit the dis-persion process of pollutants Although the ambient windspeed of 2200 LST was higher than that of 1400 LST thepollution could be more serious at 2200 LST with the samepoint source For example in the P1 point source experimentthe polluted area with concentration higher than 01 ppmwassmaller at night (Figures 8(a) and 8(c)) which reflected thatthe diffusion ability was weaker at that moment and morepollutants were trapped in the vortex on the leeward side ofbuilding-A

For the P2 point source experiment as the wind speedincreased the shape of pollution plume was changed a littleand at the height of 25m more pollutants were transportedalong the channel formed by the buildings located on thenorth of P2 Unlike P1 placing on the leeward side building

the P2 point source was set up in a more open area the pollu-tion of P2 was dominated by the convection process ratherthan the turbulent diffusion process Therefore comparingto the daytime unstable situation as wind speed increasedthe convection of the pollutants strengthened and then thepollution was relaxed a little at night (Figures 8(b) and 8(d))

In short it was found that buildings may alter the flowand concentration fields significantly The position of thepoint source had significant influences on the concentrationpattern Comparing the flow and dispersion pattern at twomoments it was found that the convection and turbulentdiffusion were the two important processes to determinethe pollution serious level Within the nocturnal stableatmospheric boundary structure although the ambient windspeed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

10 Advances in Meteorology

42 Simulation Results in Summer

421 Simulation of WRF Summer Experiment Figure 3(b)showed the observed sea level pressure field at 0800 LST 13August 2012 Similar to the winter case the Shenyang areawas under the control of this high pressure system with weaksynoptic system

Figures 4(c) and 4(d) exhibited the diurnal variationsof the observed and simulated 2-m temperature and 10-mwind speed to examine the WRF output The simulatedtemperature was a little lower than observed one at nightand the temperature during the daytime was simulated wellDespite the fact that the simulated wind speed was slightlyhigher the diurnal variation of the wind speed was simulatedwell On the whole the simulation result in summer wasbetter than that in winter

The 10-m wind vector fields and 2-m temperature fieldsof the innermost WRF domain on 16th of February 2012were shown in Figure 9 At 0200 LST the main directionof the wind was northeast while the wind turned to northat 0600 LST The wind speed increased as the land surfacewas heated by the sun It was noted that at 1800 LST thewind direction within the built-up areas of Shenyang wasdifferent from that in the suburb area the wind in the built-up areas was northwestern while the wind in the suburb areawas northern At 2200 LST the wind turned to north in thesimulation region We can also obviously find the urban heatisland effect in Shenyang at 0200 LST 1800 LST and 2200 LSTthe 2-m temperature over the built-up area was significantlyhigher than that of the suburb area

The potential temperature profile height-time section ofthe potential temperature profile and time series of boundarylayer height simulated by WRF were given in Figure 6 Thesurface-based inversion formed at 0400 LST and the intensityof inversion below the height of 500m was 23 K per 100mheight which was stronger than the inversion that happenedin winter at the same time and the depth of the inversionlayer was also thicker than that of winter (Figures 6(a) and6(b)) At 0800 LST since the ground was warmed by thesunlight a thin mixed layer was generated near ground andthe temperature inversion was detached from the ground atthe height of 250m After 0800 LST the low-level inversionlayer disappeared gradually at 1200 LST a mixed layer wasformed in the lower atmosphere from ground to the heightof 700m (Figure 6(b)) In the afternoon the mixed layerextended well to 15 km height (Figure 6(d)) favoring thevertical dilution of pollutant At night the ground was cooledby the nocturnal radiation causing the generation of theinversion stable layer near the ground Comparing to thenocturnal stable layer of the winter case the boundary layerheight of the summer experiment was lower from 0000 LSTto 0600 LST because of the calm ambient wind background(Figures 6(c) and 6(d))

422 Simulation of CFD Experiments in Summer Similarto the winter CFD numerical experiments two experi-ments with different atmospheric boundary structures weredesigned at 1400 LST (unstable case) and 2200 LST (stablecase)

Figure 10 illustrated the simulated concentration (ppm)and wind vector fields at different height at 1400 LST on 13thof August when the ambient wind direction was north Itwas noted that two counterclockwise vortices formed behindbuilding-A which was a typical double-eddy circulationreported by Hunter et al [44] and Zhang et al [45] Compar-ing to the wind vector field at 119911 = 25m the wind vector fieldof 225mwasmuch simpler and the north flowwas dominantin most of the region

At the lower level the distributions of pollutant concen-tration were consistent with the flow patternWhen the pointsourcewas located at P1 or P2 the pollutantswere transportedand trapped in the circulations of the two vortexes behindbuilding-A

Comparing the concentration fields of point sourcesP1 and P2 at two heights it was interesting to find thatthe concentration within the red rectangle in Figure 10 washigher at the height of 225m than the lower level (25mheight) The phenomenon can be explained by the windfields at different height At the height of 25m since redrectangle region was surrounded by buildings where thewind fields were detached from the ambient boundary windand were dominant by the east wind therefore the pollutantreleased from the northern P1 and P2 point sources cannotbe transported to this region directly In the contrary at theheight of 225m the red rectangle regionwas dominant by thenorth wind therefore the pollutant can be easily transportedthere

At 2200 LST when the south ambient wind blew a quitedifferent flow pattern was presented within the built-up area(Figure 11) compared to that of 1400 LST A strong divergencezone can be found in the south of building-A at the heightof 25m indicated by the red dashed rectangle in Figure 11When the airflowblew from the south a typical step-up notchwas formed by building-A (81m) and building-B (24m) asthe vertical wind field presented in Figure 12 the south inletwind was blocked by the taller building (building-A) anddescended along the windward wall of building-A and thendiverged near the ground

At the lower level the wind field around the point sources(P1 and P2) was totally rearranged by the effects of thebuildings around At the height of 225m since the sparserbuilding distribution the wind field was more close to theambient wind Therefore the wind fields of the height of25m and 225m were quite different as well as the pollutantdistributions At 119911 = 25m most of the pollutant releasedfrom P1 and P2 source was transported to south by thedivergence zone formed on the south side building-A

In these two cases it was found that the change of theambient wind direction can significantly affect the flow fieldsand pollutant distributions within the building cluster

5 Discussion and Conclusions

This study examined urban airflow and dispersion patternof pollutant released from hypothetical sources in North-eastern University of Shenyang China by using a WRF-CFD coupled model Two WRF numerical experiments

Advances in Meteorology 11

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(a)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(b)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(c)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(d)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(e)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(f)

Figure 9 The 10-m wind vector fields and 2-m temperature fields of Shenyang on 13th of August 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

12 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

(c)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

01

05

1

25

5

10

20

35

50

(d)

Figure 10 Simulated concentration (ppm) and wind vector fields at 1400 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

(Summer-Run and Winter-Run) were performed to studythe typical features of the atmospheric boundary layer struc-tures of different season Then the coupled WRF-CFD wasused to study how the atmospheric boundary structureambient wind and source position affect the wind fieldand pollutant distribution within the built-up areas It wasfound that the pollutant dispersion pattern and the pollutiondegree dispersion were complicated in the presence of realbuilding clusters and under varying atmospheric bound-ary structures ambient wind and locations of pollutionsources

From this preliminary numerical study it was found thatthe atmospheric boundary structure played a crucial role onthe pollution within the building cluster which determinedthe potential turbulent diffusion ability of the atmosphericsurface layer For example within a nocturnal stable atmo-spheric boundary condition although the ambient wind

speed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

The change of the ambient wind direction can signifi-cantly affect the dispersion pattern of pollutants which was amore sensitive factor than the ambient wind speedThereforewhen a building cluster was designed it was important toconsider the frequency of the ambient wind direction there

Under a given atmospheric state the location of thepollution source would dramatically determine the pollutionpatterns within the built-up areasWhen the pollutant sourcewas set up on the leeward side of the building the pollutantdispersion pattern was dominated by turbulent diffusion pro-cess which was affected by atmospheric boundary structureswhile the convection process dominated when the pollutantsource was set up in a more open area Besides that thedistribution of pollutant concentrationwas driven by the flowpattern

Advances in Meteorology 13

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

A

B

3

Reference vector

A

B

(a)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

B

(b)

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

A

(c)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

(d)

Figure 11 Simulated concentration (ppm) and wind vector fields at 2200 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

A

B

90

60

30

0

Z(m

)

Y (m)6005004003002001000

Reference vector3

Figure 12 The vertical plane of the wind vector field across 119883 =325m

Finally it should be noted that the wind fields anddispersion patterns within the building clusters were com-plicated which cannot be obtained from the ambient wind

TheWRF-CFD numerical evaluation can be used as a reliablemethod to understand the complicated flow and dispersionwithin the built-up areas

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is supported by the China Meteorological Admin-istration Special Public Welfare Research Fund under Grantno GYHY201106033 and the National Natural Science Foun-dation of China under Grant no 41175004

14 Advances in Meteorology

References

[1] H R Olesen R Berkowicz M Ketzel and P Loslashfstroslashm ldquoVal-idation of OML AERMODPRIME and MISKAM using theThompson wind-tunnel dataset for simple stack-building con-figurationsrdquo Boundary-LayerMeteorology vol 131 no 1 pp 73ndash83 2009

[2] R S Thompson ldquoBuilding amplification factors for sourcesnear buildings a wind-tunnel studyrdquo Atmospheric EnvironmentPart A General Topics vol 27 no 15 pp 2313ndash2325 1993

[3] A F Stein and B M Toselli ldquoStreet level air pollution in Cor-doba City ArgentinardquoAtmospheric Environment vol 30 no 20pp 3491ndash3495 1996

[4] RWMacDonald R F Griffiths and S C Cheah ldquoField exper-iments of dispersion through regular arrays of cubic structuresrdquoAtmospheric Environment vol 31 no 6 pp 783ndash795 1997

[5] R W Macdonald R F Griffiths and D J Hall ldquoA comparisonof results from scaled field and wind tunnel modelling ofdispersion in arrays of obstaclesrdquoAtmospheric Environment vol32 no 22 pp 3845ndash3862 1998

[6] M Pavageau andM Schatzmann ldquoWind tunnel measurementsof concentration fluctuations in an urban street canyonrdquo Atmo-spheric Environment vol 33 no 24-25 pp 3961ndash3971 1999

[7] P Kastner-Klein and E J Plate ldquoWind-tunnel study of concen-tration fields in street canyonsrdquo Atmospheric Environment vol33 no 24-25 pp 3973ndash3979 1999

[8] I Mavroidis R F Griffiths and D J Hall ldquoField and windtunnel investigations of plume dispersion around single surfaceobstaclesrdquo Atmospheric Environment vol 37 no 21 pp 2903ndash2918 2003

[9] DDelaunay D Lakehal C Barre andC Sacre ldquoNumerical andwind tunnel simulation of gas dispersion around a rectangularbuildingrdquo Journal ofWind Engineeringamp Industrial Aerodynam-ics vol 67-68 pp 721ndash732 1997

[10] I R Cowan I P Castro and A G Robins ldquoNumericalconsiderations for simulations of flow and dispersion aroundbuildingsrdquo Journal of Wind Engineering and Industrial Aerody-namics vol 67-68 pp 535ndash545 1997

[11] J J Baik and J J Kim ldquoOn the escape of pollutants from urbanstreet canyonsrdquo Atmospheric Environment vol 36 no 3 pp527ndash536 2002

[12] K Nazridoust and G Ahmadi ldquoAirflow and pollutant transportin street canyonsrdquo Journal of Wind Engineering and IndustrialAerodynamics vol 94 no 6 pp 491ndash522 2006

[13] Y Tominaga SMurakami andAMochida ldquoCFDprediction ofgaseous diffusion around a cubic model using a dynamic mixedSGSmodel based on composite grid techniquerdquo Journal ofWindEngineering and Industrial Aerodynamics vol 67-68 pp 827ndash841 1997

[14] K Sada and A Sato ldquoNumerical calculation of flow andstack-gas concentration fluctuation around a cubical buildingrdquoAtmospheric Environment vol 36 no 35 pp 5527ndash5534 2002

[15] X-X Li C-H Liu and D Y C Leung ldquoLarge-eddy simulationof flow and pollutant dispersion in high-aspect-ratio urbanstreet canyons with wall modelrdquo Boundary-Layer Meteorologyvol 129 no 2 pp 249ndash268 2008

[16] M Tewari H Kusaka F Chen et al ldquoImpact of couplinga microscale computational fluid dynamics model with amesoscale model on urban scale contaminant transport anddispersionrdquo Atmospheric Research vol 96 no 4 pp 656ndash6642010

[17] Y S Liu S G Miao C L Zhang G X Cui and Z S ZhangldquoStudy on micro-atmospheric environment by coupling largeeddy simulation with mesoscale modelrdquo Journal of Wind Engi-neering amp Industrial Aerodynamics vol 107-108 pp 106ndash1172012

[18] Y Miao S Liu B Chen B Zhang S Wang and S Li ldquoSimu-lating urban flow and dispersion in Beijing by coupling a CFDmodel with theWRFmodelrdquoAdvances in Atmospheric Sciencesvol 30 no 6 pp 1663ndash1678 2013

[19] X Fang W Jiang S Miao et al ldquoThe multi-scale numericalmodeling system for research on the relationship betweenurban planning and meteorological environmentrdquo Advances inAtmospheric Sciences vol 21 no 1 pp 103ndash112 2004

[20] Y C Miao S H Liu H Zheng et al ldquoA multi-scale urbanatmospheric dispersion model for emergency managementrdquoAdvances in Atmospheric Sciences vol 31 no 6 pp 1353ndash13652014

[21] S Miao W Jiang X Wang and W Guo ldquoImpact assessmentof urban meteorology and the atmospheric environment usingurban sub-domain planningrdquoBoundary-LayerMeteorology vol118 no 1 pp 133ndash150 2006

[22] OpenCFD OpenFOAM The Open Source Computational FluidDynamics (CFD) Toolbox 2008 httpwwwopencfdcoukopenfoam

[23] J H Ferziger and M Peric Computational Methods for FluidDynamics Springer Berlin Germany 3rd edition 2001

[24] Z I Janjic ldquoThe step-mountain coordinate physical packagerdquoMonthly Weather Review vol 118 no 7 pp 1429ndash1443 1990

[25] Z I Janjic ldquoThe step-mountain eta coordinate model furtherdevelopments of the convection viscous sublayer and turbu-lence closure schemesrdquoMonthlyWeather Review vol 122 no 5pp 927ndash945 1994

[26] E J Mlawer S J Taubman P D Brown M J Iacono and S AClough ldquoRadiative transfer for inhomogeneous atmospheresRRTM a validated correlated-k model for the longwaverdquoJournal of Geophysical Research Atmospheres vol 102 no 14pp 16663ndash16682 1997

[27] J Dudhia ldquoNumerical study of convection observed dur-ing the winter monsoon experiment using a mesoscale two-dimensionalmodelrdquo Journal of theAtmospheric Sciences vol 46no 20 pp 3077ndash3107 1989

[28] S-Y Hong J Dudhia and S-H Chen ldquoA revised approach toice microphysical processes for the bulk parameterization ofclouds and precipitationrdquoMonthlyWeather Review vol 132 no1 pp 103ndash120 2004

[29] J S Kain ldquoThe Kain Fritsch convective parameterization anupdaterdquo Journal of Applied Meteorology vol 43 no 1 pp 170ndash181 2004

[30] F Chen and J Dudhia ldquoCoupling and advanced land surface-hydrology model with the Penn State-NCAR MM5 modelingsystem Part I model implementation and sensitivityrdquoMonthlyWeather Review vol 129 no 4 pp 569ndash585 2001

[31] H Kusaka H Kondo Y Kikegawa and F Kimura ldquoA simplesingle-layer urban canopy model for atmospheric modelscomparison with multi-layer and slab modelsrdquo Boundary-LayerMeteorology vol 101 no 3 pp 329ndash358 2001

[32] H Kusaka and F Kimura ldquoCoupling a single-layer urbancanopy model with a simple atmospheric model impact onurban heat island simulation for an idealized caserdquo Journal of theMeteorological Society of Japan vol 82 no 1 pp 67ndash80 2004

Advances in Meteorology 15

[33] B Grisogono and J Oerlemans ldquoJustifying the WKB approxi-mation in pure katabatic flowsrdquo Tellus A Dynamic Meteorologyand Oceanography vol 54 no 5 pp 453ndash462 2002

[34] A Jericevic L Kraljevic B Grisogono H Fagerli and Z Vece-naj ldquoParameterization of vertical diffusion and the atmosphericboundary layer height determination in the EMEP modelrdquoAtmospheric Chemistry and Physics vol 10 no 2 pp 341ndash3642010

[35] C Bicheng L ShuhuaM Yucong et al ldquoConstruction and vali-dation of a computational fluid dynamics approach for flow anddispersion modeling in urban areardquo Journal of MeteorologicalResearch vol 27 no 6 pp 923ndash941 2013

[36] C Liqiang and Y Hongbin ldquoSynoptic patterns of regional airpollution in Liaoning Provincerdquo Environmental Pollution ampControl vol 28 no 6 pp 435ndash451 2006 (Chinese)

[37] S A Adachi H KusakaM G Duda et al ldquoImprovement of thesingle-layer UCM in the WRF modelrdquo in Proceedings of the 8thInternational Conference on Urban Climates (ICUC8 rsquo12) 2012

[38] G Roux Y Liu L D Monache et al ldquoVerification of highresolution WRF-RTFDDA surface forecasts over mountainsand plainsrdquo Proceedings of the 10th WRF Usersrsquo Workshop pp20ndash23 2009

[39] S Shimada T Ohsawa S Chikaoka et al ldquoAccuracy of the windspeed profile in the lower PBL as simulated by theWRFmodelrdquoSola vol 7 pp 109ndash112 2011

[40] P A Jimenez and J Dudhia ldquoImproving the representation ofresolved and unresolved topographic effects on surface wind inthe wrf modelrdquo Journal of AppliedMeteorology and Climatologyvol 51 no 2 pp 300ndash316 2012

[41] Z I Janjic ldquoNonsingular implementation of theMellor-Yamadalevel 25 scheme in the NCEP Meso modelrdquo NOAANWSNCEP Office Note 437 2001

[42] X-M Hu J W Nielsen-Gammon and F Zhang ldquoEvaluationof three planetary boundary layer schemes in the WRF modelrdquoJournal of Applied Meteorology and Climatology vol 49 no 9pp 1831ndash1844 2010

[43] J W Nielsen-Gammon C L Powell M J Mahoney et alldquoMultisensor estimation of mixing heights over a coastal cityrdquoJournal of Applied Meteorology and Climatology vol 47 no 1pp 27ndash43 2008

[44] L J Hunter G T Johnson and I D Watson ldquoAn investigationof three-dimensional characteristics of flow regimes withinthe urban canyonrdquo Atmospheric Environment Part B UrbanAtmosphere vol 26 no 4 pp 425ndash432 1992

[45] Y Q Zhang S P Arya and W H Snyder ldquoA comparisonof numerical and physical modeling of stable atmosphericflow and dispersion around a cubical buildingrdquo AtmosphericEnvironment vol 30 no 8 pp 1327ndash1345 1996

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

6 Advances in Meteorology

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(a)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

minus16

minus15

minus14

minus13

minus12

minus11

minus10

minus9

minus86

Reference vector

Tem

pera

ture

2m

(∘C)

(b)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N123

∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(c)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

minus16

minus15

minus14

minus13

minus12

minus11

minus10

minus9

minus8

6

Reference vector

Tem

pera

ture

2m

(∘C)

(d)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(e)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

minus16

minus15

minus14

minus13

minus12

minus11

minus10

minus9

minus86

Reference vectorTe

mpe

ratu

re2

m (∘

C)

(f)

Figure 5The 10-m wind vector fields and 2-m temperature fields of Shenyang on 16th of February 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

Advances in Meteorology 7

08 LST04 LST

2500

2000

1500

1000

500

0

255 258 261 264 267 270 273

Hei

ght (

m)

Potential temperature (K)

20 LST16 LST12 LST

(a)

2500

2000

1500

1000

500

0

Hei

ght (

m)

Potential temperature (K)285 288 291 294 297 300 303 306

08 LST04 LST

20 LST16 LST12 LST

(b)

1600

1400

1200

1000

800

600

400

200

0

0600 1400 2200Time

PBL

heig

ht (m

)

(c)

14000600 2200Time

1600

1400

1200

1000

800

600

400

200

0

PBL

heig

ht (m

)

(d)

400

8001200

20001600

0 4 8 12 16 20

Time (hour)

Hei

ght (

m)

260

262

264

266

268

270

272

Tem

pera

ture

(K)

(e)

400

8001200

20001600

Hei

ght (

m)

288

292

296

300

304

0 4 8 12 16 20

Time (hour)

Tem

pera

ture

(K)

(f)

Figure 6 The simulated boundary layer structure of WRF (a b) potential temperature profile (c d) diurnal variation of boundary layerheight (e f) height-time section of potential temperature (a c e) simulation on 16 February 2012 (b d f) simulation on 13 August 2012

8 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(c)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(d)

Figure 7 Simulated concentration (ppm) and wind vector fields at 1400 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

stable nocturnal boundary layer was established at 2200 LSTwith a lower boundary layer height (about 300 m)

Figure 7 exhibited the simulated concentration (ppm)and wind vector fields for two heights at 1400 LST on 16th ofFebruary At this moment the ambient wind direction givenby the WRF model was northwest and the speed was about35m sminus1 both at 119911 = 25m and 119911 = 225m At 119911 = 25mwind vectors within the buildings were quite different fromthe free wind vectors on the boundary regions under theinfluences of the buildings It was particularly obvious in thesouthern part of the build-up regions where the distributionof the buildings was denser than the other areas When theairflow passed through the building-A two lee side vortexeswere established a strong one was on the southern lee sideof the building-A and the other weak one was on the eastAnd wind speed around the edge of building-A was fastest inthe build-up area Since the building distribution was sparser

at the height of 225m the wind field there was strongerand simpler The two vortexes still existed on the lee sideof building-A Besides that at the height of 225m most ofwind vectors within the building followed the ambient winddirection

At 119911 = 25m when the point source was located at P1driven by the vortex on the lee side of building-A a pollutantplume with concentrations higher than 5 ppm extended asan ellipse-pattern and most of the pollutants were dispersedtoward the southeast (Figure 7(a)) The point source P2 waslocated at a more open area thus the pollutant concentrationwas high only at the southeast of the source due to theblock effect of the building there (Figure 7(b)) Similar to thewind vector fields the concentration field at 119911 = 225m wassimpler than that of lower level most of the pollutants weretransported by the ambient wind direction

Advances in Meteorology 9

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

(c)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(d)

Figure 8 Simulated concentration (ppm) and wind vector fields at 2200 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

At 2200 LST a typical nocturnal stable layer was formednear the surface (Figure 6(e)) which may inhibit the dis-persion process of pollutants Although the ambient windspeed of 2200 LST was higher than that of 1400 LST thepollution could be more serious at 2200 LST with the samepoint source For example in the P1 point source experimentthe polluted area with concentration higher than 01 ppmwassmaller at night (Figures 8(a) and 8(c)) which reflected thatthe diffusion ability was weaker at that moment and morepollutants were trapped in the vortex on the leeward side ofbuilding-A

For the P2 point source experiment as the wind speedincreased the shape of pollution plume was changed a littleand at the height of 25m more pollutants were transportedalong the channel formed by the buildings located on thenorth of P2 Unlike P1 placing on the leeward side building

the P2 point source was set up in a more open area the pollu-tion of P2 was dominated by the convection process ratherthan the turbulent diffusion process Therefore comparingto the daytime unstable situation as wind speed increasedthe convection of the pollutants strengthened and then thepollution was relaxed a little at night (Figures 8(b) and 8(d))

In short it was found that buildings may alter the flowand concentration fields significantly The position of thepoint source had significant influences on the concentrationpattern Comparing the flow and dispersion pattern at twomoments it was found that the convection and turbulentdiffusion were the two important processes to determinethe pollution serious level Within the nocturnal stableatmospheric boundary structure although the ambient windspeed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

10 Advances in Meteorology

42 Simulation Results in Summer

421 Simulation of WRF Summer Experiment Figure 3(b)showed the observed sea level pressure field at 0800 LST 13August 2012 Similar to the winter case the Shenyang areawas under the control of this high pressure system with weaksynoptic system

Figures 4(c) and 4(d) exhibited the diurnal variationsof the observed and simulated 2-m temperature and 10-mwind speed to examine the WRF output The simulatedtemperature was a little lower than observed one at nightand the temperature during the daytime was simulated wellDespite the fact that the simulated wind speed was slightlyhigher the diurnal variation of the wind speed was simulatedwell On the whole the simulation result in summer wasbetter than that in winter

The 10-m wind vector fields and 2-m temperature fieldsof the innermost WRF domain on 16th of February 2012were shown in Figure 9 At 0200 LST the main directionof the wind was northeast while the wind turned to northat 0600 LST The wind speed increased as the land surfacewas heated by the sun It was noted that at 1800 LST thewind direction within the built-up areas of Shenyang wasdifferent from that in the suburb area the wind in the built-up areas was northwestern while the wind in the suburb areawas northern At 2200 LST the wind turned to north in thesimulation region We can also obviously find the urban heatisland effect in Shenyang at 0200 LST 1800 LST and 2200 LSTthe 2-m temperature over the built-up area was significantlyhigher than that of the suburb area

The potential temperature profile height-time section ofthe potential temperature profile and time series of boundarylayer height simulated by WRF were given in Figure 6 Thesurface-based inversion formed at 0400 LST and the intensityof inversion below the height of 500m was 23 K per 100mheight which was stronger than the inversion that happenedin winter at the same time and the depth of the inversionlayer was also thicker than that of winter (Figures 6(a) and6(b)) At 0800 LST since the ground was warmed by thesunlight a thin mixed layer was generated near ground andthe temperature inversion was detached from the ground atthe height of 250m After 0800 LST the low-level inversionlayer disappeared gradually at 1200 LST a mixed layer wasformed in the lower atmosphere from ground to the heightof 700m (Figure 6(b)) In the afternoon the mixed layerextended well to 15 km height (Figure 6(d)) favoring thevertical dilution of pollutant At night the ground was cooledby the nocturnal radiation causing the generation of theinversion stable layer near the ground Comparing to thenocturnal stable layer of the winter case the boundary layerheight of the summer experiment was lower from 0000 LSTto 0600 LST because of the calm ambient wind background(Figures 6(c) and 6(d))

422 Simulation of CFD Experiments in Summer Similarto the winter CFD numerical experiments two experi-ments with different atmospheric boundary structures weredesigned at 1400 LST (unstable case) and 2200 LST (stablecase)

Figure 10 illustrated the simulated concentration (ppm)and wind vector fields at different height at 1400 LST on 13thof August when the ambient wind direction was north Itwas noted that two counterclockwise vortices formed behindbuilding-A which was a typical double-eddy circulationreported by Hunter et al [44] and Zhang et al [45] Compar-ing to the wind vector field at 119911 = 25m the wind vector fieldof 225mwasmuch simpler and the north flowwas dominantin most of the region

At the lower level the distributions of pollutant concen-tration were consistent with the flow patternWhen the pointsourcewas located at P1 or P2 the pollutantswere transportedand trapped in the circulations of the two vortexes behindbuilding-A

Comparing the concentration fields of point sourcesP1 and P2 at two heights it was interesting to find thatthe concentration within the red rectangle in Figure 10 washigher at the height of 225m than the lower level (25mheight) The phenomenon can be explained by the windfields at different height At the height of 25m since redrectangle region was surrounded by buildings where thewind fields were detached from the ambient boundary windand were dominant by the east wind therefore the pollutantreleased from the northern P1 and P2 point sources cannotbe transported to this region directly In the contrary at theheight of 225m the red rectangle regionwas dominant by thenorth wind therefore the pollutant can be easily transportedthere

At 2200 LST when the south ambient wind blew a quitedifferent flow pattern was presented within the built-up area(Figure 11) compared to that of 1400 LST A strong divergencezone can be found in the south of building-A at the heightof 25m indicated by the red dashed rectangle in Figure 11When the airflowblew from the south a typical step-up notchwas formed by building-A (81m) and building-B (24m) asthe vertical wind field presented in Figure 12 the south inletwind was blocked by the taller building (building-A) anddescended along the windward wall of building-A and thendiverged near the ground

At the lower level the wind field around the point sources(P1 and P2) was totally rearranged by the effects of thebuildings around At the height of 225m since the sparserbuilding distribution the wind field was more close to theambient wind Therefore the wind fields of the height of25m and 225m were quite different as well as the pollutantdistributions At 119911 = 25m most of the pollutant releasedfrom P1 and P2 source was transported to south by thedivergence zone formed on the south side building-A

In these two cases it was found that the change of theambient wind direction can significantly affect the flow fieldsand pollutant distributions within the building cluster

5 Discussion and Conclusions

This study examined urban airflow and dispersion patternof pollutant released from hypothetical sources in North-eastern University of Shenyang China by using a WRF-CFD coupled model Two WRF numerical experiments

Advances in Meteorology 11

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(a)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(b)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(c)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(d)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(e)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(f)

Figure 9 The 10-m wind vector fields and 2-m temperature fields of Shenyang on 13th of August 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

12 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

(c)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

01

05

1

25

5

10

20

35

50

(d)

Figure 10 Simulated concentration (ppm) and wind vector fields at 1400 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

(Summer-Run and Winter-Run) were performed to studythe typical features of the atmospheric boundary layer struc-tures of different season Then the coupled WRF-CFD wasused to study how the atmospheric boundary structureambient wind and source position affect the wind fieldand pollutant distribution within the built-up areas It wasfound that the pollutant dispersion pattern and the pollutiondegree dispersion were complicated in the presence of realbuilding clusters and under varying atmospheric bound-ary structures ambient wind and locations of pollutionsources

From this preliminary numerical study it was found thatthe atmospheric boundary structure played a crucial role onthe pollution within the building cluster which determinedthe potential turbulent diffusion ability of the atmosphericsurface layer For example within a nocturnal stable atmo-spheric boundary condition although the ambient wind

speed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

The change of the ambient wind direction can signifi-cantly affect the dispersion pattern of pollutants which was amore sensitive factor than the ambient wind speedThereforewhen a building cluster was designed it was important toconsider the frequency of the ambient wind direction there

Under a given atmospheric state the location of thepollution source would dramatically determine the pollutionpatterns within the built-up areasWhen the pollutant sourcewas set up on the leeward side of the building the pollutantdispersion pattern was dominated by turbulent diffusion pro-cess which was affected by atmospheric boundary structureswhile the convection process dominated when the pollutantsource was set up in a more open area Besides that thedistribution of pollutant concentrationwas driven by the flowpattern

Advances in Meteorology 13

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

A

B

3

Reference vector

A

B

(a)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

B

(b)

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

A

(c)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

(d)

Figure 11 Simulated concentration (ppm) and wind vector fields at 2200 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

A

B

90

60

30

0

Z(m

)

Y (m)6005004003002001000

Reference vector3

Figure 12 The vertical plane of the wind vector field across 119883 =325m

Finally it should be noted that the wind fields anddispersion patterns within the building clusters were com-plicated which cannot be obtained from the ambient wind

TheWRF-CFD numerical evaluation can be used as a reliablemethod to understand the complicated flow and dispersionwithin the built-up areas

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is supported by the China Meteorological Admin-istration Special Public Welfare Research Fund under Grantno GYHY201106033 and the National Natural Science Foun-dation of China under Grant no 41175004

14 Advances in Meteorology

References

[1] H R Olesen R Berkowicz M Ketzel and P Loslashfstroslashm ldquoVal-idation of OML AERMODPRIME and MISKAM using theThompson wind-tunnel dataset for simple stack-building con-figurationsrdquo Boundary-LayerMeteorology vol 131 no 1 pp 73ndash83 2009

[2] R S Thompson ldquoBuilding amplification factors for sourcesnear buildings a wind-tunnel studyrdquo Atmospheric EnvironmentPart A General Topics vol 27 no 15 pp 2313ndash2325 1993

[3] A F Stein and B M Toselli ldquoStreet level air pollution in Cor-doba City ArgentinardquoAtmospheric Environment vol 30 no 20pp 3491ndash3495 1996

[4] RWMacDonald R F Griffiths and S C Cheah ldquoField exper-iments of dispersion through regular arrays of cubic structuresrdquoAtmospheric Environment vol 31 no 6 pp 783ndash795 1997

[5] R W Macdonald R F Griffiths and D J Hall ldquoA comparisonof results from scaled field and wind tunnel modelling ofdispersion in arrays of obstaclesrdquoAtmospheric Environment vol32 no 22 pp 3845ndash3862 1998

[6] M Pavageau andM Schatzmann ldquoWind tunnel measurementsof concentration fluctuations in an urban street canyonrdquo Atmo-spheric Environment vol 33 no 24-25 pp 3961ndash3971 1999

[7] P Kastner-Klein and E J Plate ldquoWind-tunnel study of concen-tration fields in street canyonsrdquo Atmospheric Environment vol33 no 24-25 pp 3973ndash3979 1999

[8] I Mavroidis R F Griffiths and D J Hall ldquoField and windtunnel investigations of plume dispersion around single surfaceobstaclesrdquo Atmospheric Environment vol 37 no 21 pp 2903ndash2918 2003

[9] DDelaunay D Lakehal C Barre andC Sacre ldquoNumerical andwind tunnel simulation of gas dispersion around a rectangularbuildingrdquo Journal ofWind Engineeringamp Industrial Aerodynam-ics vol 67-68 pp 721ndash732 1997

[10] I R Cowan I P Castro and A G Robins ldquoNumericalconsiderations for simulations of flow and dispersion aroundbuildingsrdquo Journal of Wind Engineering and Industrial Aerody-namics vol 67-68 pp 535ndash545 1997

[11] J J Baik and J J Kim ldquoOn the escape of pollutants from urbanstreet canyonsrdquo Atmospheric Environment vol 36 no 3 pp527ndash536 2002

[12] K Nazridoust and G Ahmadi ldquoAirflow and pollutant transportin street canyonsrdquo Journal of Wind Engineering and IndustrialAerodynamics vol 94 no 6 pp 491ndash522 2006

[13] Y Tominaga SMurakami andAMochida ldquoCFDprediction ofgaseous diffusion around a cubic model using a dynamic mixedSGSmodel based on composite grid techniquerdquo Journal ofWindEngineering and Industrial Aerodynamics vol 67-68 pp 827ndash841 1997

[14] K Sada and A Sato ldquoNumerical calculation of flow andstack-gas concentration fluctuation around a cubical buildingrdquoAtmospheric Environment vol 36 no 35 pp 5527ndash5534 2002

[15] X-X Li C-H Liu and D Y C Leung ldquoLarge-eddy simulationof flow and pollutant dispersion in high-aspect-ratio urbanstreet canyons with wall modelrdquo Boundary-Layer Meteorologyvol 129 no 2 pp 249ndash268 2008

[16] M Tewari H Kusaka F Chen et al ldquoImpact of couplinga microscale computational fluid dynamics model with amesoscale model on urban scale contaminant transport anddispersionrdquo Atmospheric Research vol 96 no 4 pp 656ndash6642010

[17] Y S Liu S G Miao C L Zhang G X Cui and Z S ZhangldquoStudy on micro-atmospheric environment by coupling largeeddy simulation with mesoscale modelrdquo Journal of Wind Engi-neering amp Industrial Aerodynamics vol 107-108 pp 106ndash1172012

[18] Y Miao S Liu B Chen B Zhang S Wang and S Li ldquoSimu-lating urban flow and dispersion in Beijing by coupling a CFDmodel with theWRFmodelrdquoAdvances in Atmospheric Sciencesvol 30 no 6 pp 1663ndash1678 2013

[19] X Fang W Jiang S Miao et al ldquoThe multi-scale numericalmodeling system for research on the relationship betweenurban planning and meteorological environmentrdquo Advances inAtmospheric Sciences vol 21 no 1 pp 103ndash112 2004

[20] Y C Miao S H Liu H Zheng et al ldquoA multi-scale urbanatmospheric dispersion model for emergency managementrdquoAdvances in Atmospheric Sciences vol 31 no 6 pp 1353ndash13652014

[21] S Miao W Jiang X Wang and W Guo ldquoImpact assessmentof urban meteorology and the atmospheric environment usingurban sub-domain planningrdquoBoundary-LayerMeteorology vol118 no 1 pp 133ndash150 2006

[22] OpenCFD OpenFOAM The Open Source Computational FluidDynamics (CFD) Toolbox 2008 httpwwwopencfdcoukopenfoam

[23] J H Ferziger and M Peric Computational Methods for FluidDynamics Springer Berlin Germany 3rd edition 2001

[24] Z I Janjic ldquoThe step-mountain coordinate physical packagerdquoMonthly Weather Review vol 118 no 7 pp 1429ndash1443 1990

[25] Z I Janjic ldquoThe step-mountain eta coordinate model furtherdevelopments of the convection viscous sublayer and turbu-lence closure schemesrdquoMonthlyWeather Review vol 122 no 5pp 927ndash945 1994

[26] E J Mlawer S J Taubman P D Brown M J Iacono and S AClough ldquoRadiative transfer for inhomogeneous atmospheresRRTM a validated correlated-k model for the longwaverdquoJournal of Geophysical Research Atmospheres vol 102 no 14pp 16663ndash16682 1997

[27] J Dudhia ldquoNumerical study of convection observed dur-ing the winter monsoon experiment using a mesoscale two-dimensionalmodelrdquo Journal of theAtmospheric Sciences vol 46no 20 pp 3077ndash3107 1989

[28] S-Y Hong J Dudhia and S-H Chen ldquoA revised approach toice microphysical processes for the bulk parameterization ofclouds and precipitationrdquoMonthlyWeather Review vol 132 no1 pp 103ndash120 2004

[29] J S Kain ldquoThe Kain Fritsch convective parameterization anupdaterdquo Journal of Applied Meteorology vol 43 no 1 pp 170ndash181 2004

[30] F Chen and J Dudhia ldquoCoupling and advanced land surface-hydrology model with the Penn State-NCAR MM5 modelingsystem Part I model implementation and sensitivityrdquoMonthlyWeather Review vol 129 no 4 pp 569ndash585 2001

[31] H Kusaka H Kondo Y Kikegawa and F Kimura ldquoA simplesingle-layer urban canopy model for atmospheric modelscomparison with multi-layer and slab modelsrdquo Boundary-LayerMeteorology vol 101 no 3 pp 329ndash358 2001

[32] H Kusaka and F Kimura ldquoCoupling a single-layer urbancanopy model with a simple atmospheric model impact onurban heat island simulation for an idealized caserdquo Journal of theMeteorological Society of Japan vol 82 no 1 pp 67ndash80 2004

Advances in Meteorology 15

[33] B Grisogono and J Oerlemans ldquoJustifying the WKB approxi-mation in pure katabatic flowsrdquo Tellus A Dynamic Meteorologyand Oceanography vol 54 no 5 pp 453ndash462 2002

[34] A Jericevic L Kraljevic B Grisogono H Fagerli and Z Vece-naj ldquoParameterization of vertical diffusion and the atmosphericboundary layer height determination in the EMEP modelrdquoAtmospheric Chemistry and Physics vol 10 no 2 pp 341ndash3642010

[35] C Bicheng L ShuhuaM Yucong et al ldquoConstruction and vali-dation of a computational fluid dynamics approach for flow anddispersion modeling in urban areardquo Journal of MeteorologicalResearch vol 27 no 6 pp 923ndash941 2013

[36] C Liqiang and Y Hongbin ldquoSynoptic patterns of regional airpollution in Liaoning Provincerdquo Environmental Pollution ampControl vol 28 no 6 pp 435ndash451 2006 (Chinese)

[37] S A Adachi H KusakaM G Duda et al ldquoImprovement of thesingle-layer UCM in the WRF modelrdquo in Proceedings of the 8thInternational Conference on Urban Climates (ICUC8 rsquo12) 2012

[38] G Roux Y Liu L D Monache et al ldquoVerification of highresolution WRF-RTFDDA surface forecasts over mountainsand plainsrdquo Proceedings of the 10th WRF Usersrsquo Workshop pp20ndash23 2009

[39] S Shimada T Ohsawa S Chikaoka et al ldquoAccuracy of the windspeed profile in the lower PBL as simulated by theWRFmodelrdquoSola vol 7 pp 109ndash112 2011

[40] P A Jimenez and J Dudhia ldquoImproving the representation ofresolved and unresolved topographic effects on surface wind inthe wrf modelrdquo Journal of AppliedMeteorology and Climatologyvol 51 no 2 pp 300ndash316 2012

[41] Z I Janjic ldquoNonsingular implementation of theMellor-Yamadalevel 25 scheme in the NCEP Meso modelrdquo NOAANWSNCEP Office Note 437 2001

[42] X-M Hu J W Nielsen-Gammon and F Zhang ldquoEvaluationof three planetary boundary layer schemes in the WRF modelrdquoJournal of Applied Meteorology and Climatology vol 49 no 9pp 1831ndash1844 2010

[43] J W Nielsen-Gammon C L Powell M J Mahoney et alldquoMultisensor estimation of mixing heights over a coastal cityrdquoJournal of Applied Meteorology and Climatology vol 47 no 1pp 27ndash43 2008

[44] L J Hunter G T Johnson and I D Watson ldquoAn investigationof three-dimensional characteristics of flow regimes withinthe urban canyonrdquo Atmospheric Environment Part B UrbanAtmosphere vol 26 no 4 pp 425ndash432 1992

[45] Y Q Zhang S P Arya and W H Snyder ldquoA comparisonof numerical and physical modeling of stable atmosphericflow and dispersion around a cubical buildingrdquo AtmosphericEnvironment vol 30 no 8 pp 1327ndash1345 1996

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

Advances in Meteorology 7

08 LST04 LST

2500

2000

1500

1000

500

0

255 258 261 264 267 270 273

Hei

ght (

m)

Potential temperature (K)

20 LST16 LST12 LST

(a)

2500

2000

1500

1000

500

0

Hei

ght (

m)

Potential temperature (K)285 288 291 294 297 300 303 306

08 LST04 LST

20 LST16 LST12 LST

(b)

1600

1400

1200

1000

800

600

400

200

0

0600 1400 2200Time

PBL

heig

ht (m

)

(c)

14000600 2200Time

1600

1400

1200

1000

800

600

400

200

0

PBL

heig

ht (m

)

(d)

400

8001200

20001600

0 4 8 12 16 20

Time (hour)

Hei

ght (

m)

260

262

264

266

268

270

272

Tem

pera

ture

(K)

(e)

400

8001200

20001600

Hei

ght (

m)

288

292

296

300

304

0 4 8 12 16 20

Time (hour)

Tem

pera

ture

(K)

(f)

Figure 6 The simulated boundary layer structure of WRF (a b) potential temperature profile (c d) diurnal variation of boundary layerheight (e f) height-time section of potential temperature (a c e) simulation on 16 February 2012 (b d f) simulation on 13 August 2012

8 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(c)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(d)

Figure 7 Simulated concentration (ppm) and wind vector fields at 1400 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

stable nocturnal boundary layer was established at 2200 LSTwith a lower boundary layer height (about 300 m)

Figure 7 exhibited the simulated concentration (ppm)and wind vector fields for two heights at 1400 LST on 16th ofFebruary At this moment the ambient wind direction givenby the WRF model was northwest and the speed was about35m sminus1 both at 119911 = 25m and 119911 = 225m At 119911 = 25mwind vectors within the buildings were quite different fromthe free wind vectors on the boundary regions under theinfluences of the buildings It was particularly obvious in thesouthern part of the build-up regions where the distributionof the buildings was denser than the other areas When theairflow passed through the building-A two lee side vortexeswere established a strong one was on the southern lee sideof the building-A and the other weak one was on the eastAnd wind speed around the edge of building-A was fastest inthe build-up area Since the building distribution was sparser

at the height of 225m the wind field there was strongerand simpler The two vortexes still existed on the lee sideof building-A Besides that at the height of 225m most ofwind vectors within the building followed the ambient winddirection

At 119911 = 25m when the point source was located at P1driven by the vortex on the lee side of building-A a pollutantplume with concentrations higher than 5 ppm extended asan ellipse-pattern and most of the pollutants were dispersedtoward the southeast (Figure 7(a)) The point source P2 waslocated at a more open area thus the pollutant concentrationwas high only at the southeast of the source due to theblock effect of the building there (Figure 7(b)) Similar to thewind vector fields the concentration field at 119911 = 225m wassimpler than that of lower level most of the pollutants weretransported by the ambient wind direction

Advances in Meteorology 9

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

(c)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(d)

Figure 8 Simulated concentration (ppm) and wind vector fields at 2200 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

At 2200 LST a typical nocturnal stable layer was formednear the surface (Figure 6(e)) which may inhibit the dis-persion process of pollutants Although the ambient windspeed of 2200 LST was higher than that of 1400 LST thepollution could be more serious at 2200 LST with the samepoint source For example in the P1 point source experimentthe polluted area with concentration higher than 01 ppmwassmaller at night (Figures 8(a) and 8(c)) which reflected thatthe diffusion ability was weaker at that moment and morepollutants were trapped in the vortex on the leeward side ofbuilding-A

For the P2 point source experiment as the wind speedincreased the shape of pollution plume was changed a littleand at the height of 25m more pollutants were transportedalong the channel formed by the buildings located on thenorth of P2 Unlike P1 placing on the leeward side building

the P2 point source was set up in a more open area the pollu-tion of P2 was dominated by the convection process ratherthan the turbulent diffusion process Therefore comparingto the daytime unstable situation as wind speed increasedthe convection of the pollutants strengthened and then thepollution was relaxed a little at night (Figures 8(b) and 8(d))

In short it was found that buildings may alter the flowand concentration fields significantly The position of thepoint source had significant influences on the concentrationpattern Comparing the flow and dispersion pattern at twomoments it was found that the convection and turbulentdiffusion were the two important processes to determinethe pollution serious level Within the nocturnal stableatmospheric boundary structure although the ambient windspeed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

10 Advances in Meteorology

42 Simulation Results in Summer

421 Simulation of WRF Summer Experiment Figure 3(b)showed the observed sea level pressure field at 0800 LST 13August 2012 Similar to the winter case the Shenyang areawas under the control of this high pressure system with weaksynoptic system

Figures 4(c) and 4(d) exhibited the diurnal variationsof the observed and simulated 2-m temperature and 10-mwind speed to examine the WRF output The simulatedtemperature was a little lower than observed one at nightand the temperature during the daytime was simulated wellDespite the fact that the simulated wind speed was slightlyhigher the diurnal variation of the wind speed was simulatedwell On the whole the simulation result in summer wasbetter than that in winter

The 10-m wind vector fields and 2-m temperature fieldsof the innermost WRF domain on 16th of February 2012were shown in Figure 9 At 0200 LST the main directionof the wind was northeast while the wind turned to northat 0600 LST The wind speed increased as the land surfacewas heated by the sun It was noted that at 1800 LST thewind direction within the built-up areas of Shenyang wasdifferent from that in the suburb area the wind in the built-up areas was northwestern while the wind in the suburb areawas northern At 2200 LST the wind turned to north in thesimulation region We can also obviously find the urban heatisland effect in Shenyang at 0200 LST 1800 LST and 2200 LSTthe 2-m temperature over the built-up area was significantlyhigher than that of the suburb area

The potential temperature profile height-time section ofthe potential temperature profile and time series of boundarylayer height simulated by WRF were given in Figure 6 Thesurface-based inversion formed at 0400 LST and the intensityof inversion below the height of 500m was 23 K per 100mheight which was stronger than the inversion that happenedin winter at the same time and the depth of the inversionlayer was also thicker than that of winter (Figures 6(a) and6(b)) At 0800 LST since the ground was warmed by thesunlight a thin mixed layer was generated near ground andthe temperature inversion was detached from the ground atthe height of 250m After 0800 LST the low-level inversionlayer disappeared gradually at 1200 LST a mixed layer wasformed in the lower atmosphere from ground to the heightof 700m (Figure 6(b)) In the afternoon the mixed layerextended well to 15 km height (Figure 6(d)) favoring thevertical dilution of pollutant At night the ground was cooledby the nocturnal radiation causing the generation of theinversion stable layer near the ground Comparing to thenocturnal stable layer of the winter case the boundary layerheight of the summer experiment was lower from 0000 LSTto 0600 LST because of the calm ambient wind background(Figures 6(c) and 6(d))

422 Simulation of CFD Experiments in Summer Similarto the winter CFD numerical experiments two experi-ments with different atmospheric boundary structures weredesigned at 1400 LST (unstable case) and 2200 LST (stablecase)

Figure 10 illustrated the simulated concentration (ppm)and wind vector fields at different height at 1400 LST on 13thof August when the ambient wind direction was north Itwas noted that two counterclockwise vortices formed behindbuilding-A which was a typical double-eddy circulationreported by Hunter et al [44] and Zhang et al [45] Compar-ing to the wind vector field at 119911 = 25m the wind vector fieldof 225mwasmuch simpler and the north flowwas dominantin most of the region

At the lower level the distributions of pollutant concen-tration were consistent with the flow patternWhen the pointsourcewas located at P1 or P2 the pollutantswere transportedand trapped in the circulations of the two vortexes behindbuilding-A

Comparing the concentration fields of point sourcesP1 and P2 at two heights it was interesting to find thatthe concentration within the red rectangle in Figure 10 washigher at the height of 225m than the lower level (25mheight) The phenomenon can be explained by the windfields at different height At the height of 25m since redrectangle region was surrounded by buildings where thewind fields were detached from the ambient boundary windand were dominant by the east wind therefore the pollutantreleased from the northern P1 and P2 point sources cannotbe transported to this region directly In the contrary at theheight of 225m the red rectangle regionwas dominant by thenorth wind therefore the pollutant can be easily transportedthere

At 2200 LST when the south ambient wind blew a quitedifferent flow pattern was presented within the built-up area(Figure 11) compared to that of 1400 LST A strong divergencezone can be found in the south of building-A at the heightof 25m indicated by the red dashed rectangle in Figure 11When the airflowblew from the south a typical step-up notchwas formed by building-A (81m) and building-B (24m) asthe vertical wind field presented in Figure 12 the south inletwind was blocked by the taller building (building-A) anddescended along the windward wall of building-A and thendiverged near the ground

At the lower level the wind field around the point sources(P1 and P2) was totally rearranged by the effects of thebuildings around At the height of 225m since the sparserbuilding distribution the wind field was more close to theambient wind Therefore the wind fields of the height of25m and 225m were quite different as well as the pollutantdistributions At 119911 = 25m most of the pollutant releasedfrom P1 and P2 source was transported to south by thedivergence zone formed on the south side building-A

In these two cases it was found that the change of theambient wind direction can significantly affect the flow fieldsand pollutant distributions within the building cluster

5 Discussion and Conclusions

This study examined urban airflow and dispersion patternof pollutant released from hypothetical sources in North-eastern University of Shenyang China by using a WRF-CFD coupled model Two WRF numerical experiments

Advances in Meteorology 11

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(a)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(b)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(c)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(d)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(e)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(f)

Figure 9 The 10-m wind vector fields and 2-m temperature fields of Shenyang on 13th of August 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

12 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

(c)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

01

05

1

25

5

10

20

35

50

(d)

Figure 10 Simulated concentration (ppm) and wind vector fields at 1400 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

(Summer-Run and Winter-Run) were performed to studythe typical features of the atmospheric boundary layer struc-tures of different season Then the coupled WRF-CFD wasused to study how the atmospheric boundary structureambient wind and source position affect the wind fieldand pollutant distribution within the built-up areas It wasfound that the pollutant dispersion pattern and the pollutiondegree dispersion were complicated in the presence of realbuilding clusters and under varying atmospheric bound-ary structures ambient wind and locations of pollutionsources

From this preliminary numerical study it was found thatthe atmospheric boundary structure played a crucial role onthe pollution within the building cluster which determinedthe potential turbulent diffusion ability of the atmosphericsurface layer For example within a nocturnal stable atmo-spheric boundary condition although the ambient wind

speed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

The change of the ambient wind direction can signifi-cantly affect the dispersion pattern of pollutants which was amore sensitive factor than the ambient wind speedThereforewhen a building cluster was designed it was important toconsider the frequency of the ambient wind direction there

Under a given atmospheric state the location of thepollution source would dramatically determine the pollutionpatterns within the built-up areasWhen the pollutant sourcewas set up on the leeward side of the building the pollutantdispersion pattern was dominated by turbulent diffusion pro-cess which was affected by atmospheric boundary structureswhile the convection process dominated when the pollutantsource was set up in a more open area Besides that thedistribution of pollutant concentrationwas driven by the flowpattern

Advances in Meteorology 13

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

A

B

3

Reference vector

A

B

(a)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

B

(b)

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

A

(c)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

(d)

Figure 11 Simulated concentration (ppm) and wind vector fields at 2200 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

A

B

90

60

30

0

Z(m

)

Y (m)6005004003002001000

Reference vector3

Figure 12 The vertical plane of the wind vector field across 119883 =325m

Finally it should be noted that the wind fields anddispersion patterns within the building clusters were com-plicated which cannot be obtained from the ambient wind

TheWRF-CFD numerical evaluation can be used as a reliablemethod to understand the complicated flow and dispersionwithin the built-up areas

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is supported by the China Meteorological Admin-istration Special Public Welfare Research Fund under Grantno GYHY201106033 and the National Natural Science Foun-dation of China under Grant no 41175004

14 Advances in Meteorology

References

[1] H R Olesen R Berkowicz M Ketzel and P Loslashfstroslashm ldquoVal-idation of OML AERMODPRIME and MISKAM using theThompson wind-tunnel dataset for simple stack-building con-figurationsrdquo Boundary-LayerMeteorology vol 131 no 1 pp 73ndash83 2009

[2] R S Thompson ldquoBuilding amplification factors for sourcesnear buildings a wind-tunnel studyrdquo Atmospheric EnvironmentPart A General Topics vol 27 no 15 pp 2313ndash2325 1993

[3] A F Stein and B M Toselli ldquoStreet level air pollution in Cor-doba City ArgentinardquoAtmospheric Environment vol 30 no 20pp 3491ndash3495 1996

[4] RWMacDonald R F Griffiths and S C Cheah ldquoField exper-iments of dispersion through regular arrays of cubic structuresrdquoAtmospheric Environment vol 31 no 6 pp 783ndash795 1997

[5] R W Macdonald R F Griffiths and D J Hall ldquoA comparisonof results from scaled field and wind tunnel modelling ofdispersion in arrays of obstaclesrdquoAtmospheric Environment vol32 no 22 pp 3845ndash3862 1998

[6] M Pavageau andM Schatzmann ldquoWind tunnel measurementsof concentration fluctuations in an urban street canyonrdquo Atmo-spheric Environment vol 33 no 24-25 pp 3961ndash3971 1999

[7] P Kastner-Klein and E J Plate ldquoWind-tunnel study of concen-tration fields in street canyonsrdquo Atmospheric Environment vol33 no 24-25 pp 3973ndash3979 1999

[8] I Mavroidis R F Griffiths and D J Hall ldquoField and windtunnel investigations of plume dispersion around single surfaceobstaclesrdquo Atmospheric Environment vol 37 no 21 pp 2903ndash2918 2003

[9] DDelaunay D Lakehal C Barre andC Sacre ldquoNumerical andwind tunnel simulation of gas dispersion around a rectangularbuildingrdquo Journal ofWind Engineeringamp Industrial Aerodynam-ics vol 67-68 pp 721ndash732 1997

[10] I R Cowan I P Castro and A G Robins ldquoNumericalconsiderations for simulations of flow and dispersion aroundbuildingsrdquo Journal of Wind Engineering and Industrial Aerody-namics vol 67-68 pp 535ndash545 1997

[11] J J Baik and J J Kim ldquoOn the escape of pollutants from urbanstreet canyonsrdquo Atmospheric Environment vol 36 no 3 pp527ndash536 2002

[12] K Nazridoust and G Ahmadi ldquoAirflow and pollutant transportin street canyonsrdquo Journal of Wind Engineering and IndustrialAerodynamics vol 94 no 6 pp 491ndash522 2006

[13] Y Tominaga SMurakami andAMochida ldquoCFDprediction ofgaseous diffusion around a cubic model using a dynamic mixedSGSmodel based on composite grid techniquerdquo Journal ofWindEngineering and Industrial Aerodynamics vol 67-68 pp 827ndash841 1997

[14] K Sada and A Sato ldquoNumerical calculation of flow andstack-gas concentration fluctuation around a cubical buildingrdquoAtmospheric Environment vol 36 no 35 pp 5527ndash5534 2002

[15] X-X Li C-H Liu and D Y C Leung ldquoLarge-eddy simulationof flow and pollutant dispersion in high-aspect-ratio urbanstreet canyons with wall modelrdquo Boundary-Layer Meteorologyvol 129 no 2 pp 249ndash268 2008

[16] M Tewari H Kusaka F Chen et al ldquoImpact of couplinga microscale computational fluid dynamics model with amesoscale model on urban scale contaminant transport anddispersionrdquo Atmospheric Research vol 96 no 4 pp 656ndash6642010

[17] Y S Liu S G Miao C L Zhang G X Cui and Z S ZhangldquoStudy on micro-atmospheric environment by coupling largeeddy simulation with mesoscale modelrdquo Journal of Wind Engi-neering amp Industrial Aerodynamics vol 107-108 pp 106ndash1172012

[18] Y Miao S Liu B Chen B Zhang S Wang and S Li ldquoSimu-lating urban flow and dispersion in Beijing by coupling a CFDmodel with theWRFmodelrdquoAdvances in Atmospheric Sciencesvol 30 no 6 pp 1663ndash1678 2013

[19] X Fang W Jiang S Miao et al ldquoThe multi-scale numericalmodeling system for research on the relationship betweenurban planning and meteorological environmentrdquo Advances inAtmospheric Sciences vol 21 no 1 pp 103ndash112 2004

[20] Y C Miao S H Liu H Zheng et al ldquoA multi-scale urbanatmospheric dispersion model for emergency managementrdquoAdvances in Atmospheric Sciences vol 31 no 6 pp 1353ndash13652014

[21] S Miao W Jiang X Wang and W Guo ldquoImpact assessmentof urban meteorology and the atmospheric environment usingurban sub-domain planningrdquoBoundary-LayerMeteorology vol118 no 1 pp 133ndash150 2006

[22] OpenCFD OpenFOAM The Open Source Computational FluidDynamics (CFD) Toolbox 2008 httpwwwopencfdcoukopenfoam

[23] J H Ferziger and M Peric Computational Methods for FluidDynamics Springer Berlin Germany 3rd edition 2001

[24] Z I Janjic ldquoThe step-mountain coordinate physical packagerdquoMonthly Weather Review vol 118 no 7 pp 1429ndash1443 1990

[25] Z I Janjic ldquoThe step-mountain eta coordinate model furtherdevelopments of the convection viscous sublayer and turbu-lence closure schemesrdquoMonthlyWeather Review vol 122 no 5pp 927ndash945 1994

[26] E J Mlawer S J Taubman P D Brown M J Iacono and S AClough ldquoRadiative transfer for inhomogeneous atmospheresRRTM a validated correlated-k model for the longwaverdquoJournal of Geophysical Research Atmospheres vol 102 no 14pp 16663ndash16682 1997

[27] J Dudhia ldquoNumerical study of convection observed dur-ing the winter monsoon experiment using a mesoscale two-dimensionalmodelrdquo Journal of theAtmospheric Sciences vol 46no 20 pp 3077ndash3107 1989

[28] S-Y Hong J Dudhia and S-H Chen ldquoA revised approach toice microphysical processes for the bulk parameterization ofclouds and precipitationrdquoMonthlyWeather Review vol 132 no1 pp 103ndash120 2004

[29] J S Kain ldquoThe Kain Fritsch convective parameterization anupdaterdquo Journal of Applied Meteorology vol 43 no 1 pp 170ndash181 2004

[30] F Chen and J Dudhia ldquoCoupling and advanced land surface-hydrology model with the Penn State-NCAR MM5 modelingsystem Part I model implementation and sensitivityrdquoMonthlyWeather Review vol 129 no 4 pp 569ndash585 2001

[31] H Kusaka H Kondo Y Kikegawa and F Kimura ldquoA simplesingle-layer urban canopy model for atmospheric modelscomparison with multi-layer and slab modelsrdquo Boundary-LayerMeteorology vol 101 no 3 pp 329ndash358 2001

[32] H Kusaka and F Kimura ldquoCoupling a single-layer urbancanopy model with a simple atmospheric model impact onurban heat island simulation for an idealized caserdquo Journal of theMeteorological Society of Japan vol 82 no 1 pp 67ndash80 2004

Advances in Meteorology 15

[33] B Grisogono and J Oerlemans ldquoJustifying the WKB approxi-mation in pure katabatic flowsrdquo Tellus A Dynamic Meteorologyand Oceanography vol 54 no 5 pp 453ndash462 2002

[34] A Jericevic L Kraljevic B Grisogono H Fagerli and Z Vece-naj ldquoParameterization of vertical diffusion and the atmosphericboundary layer height determination in the EMEP modelrdquoAtmospheric Chemistry and Physics vol 10 no 2 pp 341ndash3642010

[35] C Bicheng L ShuhuaM Yucong et al ldquoConstruction and vali-dation of a computational fluid dynamics approach for flow anddispersion modeling in urban areardquo Journal of MeteorologicalResearch vol 27 no 6 pp 923ndash941 2013

[36] C Liqiang and Y Hongbin ldquoSynoptic patterns of regional airpollution in Liaoning Provincerdquo Environmental Pollution ampControl vol 28 no 6 pp 435ndash451 2006 (Chinese)

[37] S A Adachi H KusakaM G Duda et al ldquoImprovement of thesingle-layer UCM in the WRF modelrdquo in Proceedings of the 8thInternational Conference on Urban Climates (ICUC8 rsquo12) 2012

[38] G Roux Y Liu L D Monache et al ldquoVerification of highresolution WRF-RTFDDA surface forecasts over mountainsand plainsrdquo Proceedings of the 10th WRF Usersrsquo Workshop pp20ndash23 2009

[39] S Shimada T Ohsawa S Chikaoka et al ldquoAccuracy of the windspeed profile in the lower PBL as simulated by theWRFmodelrdquoSola vol 7 pp 109ndash112 2011

[40] P A Jimenez and J Dudhia ldquoImproving the representation ofresolved and unresolved topographic effects on surface wind inthe wrf modelrdquo Journal of AppliedMeteorology and Climatologyvol 51 no 2 pp 300ndash316 2012

[41] Z I Janjic ldquoNonsingular implementation of theMellor-Yamadalevel 25 scheme in the NCEP Meso modelrdquo NOAANWSNCEP Office Note 437 2001

[42] X-M Hu J W Nielsen-Gammon and F Zhang ldquoEvaluationof three planetary boundary layer schemes in the WRF modelrdquoJournal of Applied Meteorology and Climatology vol 49 no 9pp 1831ndash1844 2010

[43] J W Nielsen-Gammon C L Powell M J Mahoney et alldquoMultisensor estimation of mixing heights over a coastal cityrdquoJournal of Applied Meteorology and Climatology vol 47 no 1pp 27ndash43 2008

[44] L J Hunter G T Johnson and I D Watson ldquoAn investigationof three-dimensional characteristics of flow regimes withinthe urban canyonrdquo Atmospheric Environment Part B UrbanAtmosphere vol 26 no 4 pp 425ndash432 1992

[45] Y Q Zhang S P Arya and W H Snyder ldquoA comparisonof numerical and physical modeling of stable atmosphericflow and dispersion around a cubical buildingrdquo AtmosphericEnvironment vol 30 no 8 pp 1327ndash1345 1996

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

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MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

8 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(c)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(d)

Figure 7 Simulated concentration (ppm) and wind vector fields at 1400 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

stable nocturnal boundary layer was established at 2200 LSTwith a lower boundary layer height (about 300 m)

Figure 7 exhibited the simulated concentration (ppm)and wind vector fields for two heights at 1400 LST on 16th ofFebruary At this moment the ambient wind direction givenby the WRF model was northwest and the speed was about35m sminus1 both at 119911 = 25m and 119911 = 225m At 119911 = 25mwind vectors within the buildings were quite different fromthe free wind vectors on the boundary regions under theinfluences of the buildings It was particularly obvious in thesouthern part of the build-up regions where the distributionof the buildings was denser than the other areas When theairflow passed through the building-A two lee side vortexeswere established a strong one was on the southern lee sideof the building-A and the other weak one was on the eastAnd wind speed around the edge of building-A was fastest inthe build-up area Since the building distribution was sparser

at the height of 225m the wind field there was strongerand simpler The two vortexes still existed on the lee sideof building-A Besides that at the height of 225m most ofwind vectors within the building followed the ambient winddirection

At 119911 = 25m when the point source was located at P1driven by the vortex on the lee side of building-A a pollutantplume with concentrations higher than 5 ppm extended asan ellipse-pattern and most of the pollutants were dispersedtoward the southeast (Figure 7(a)) The point source P2 waslocated at a more open area thus the pollutant concentrationwas high only at the southeast of the source due to theblock effect of the building there (Figure 7(b)) Similar to thewind vector fields the concentration field at 119911 = 225m wassimpler than that of lower level most of the pollutants weretransported by the ambient wind direction

Advances in Meteorology 9

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

(c)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(d)

Figure 8 Simulated concentration (ppm) and wind vector fields at 2200 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

At 2200 LST a typical nocturnal stable layer was formednear the surface (Figure 6(e)) which may inhibit the dis-persion process of pollutants Although the ambient windspeed of 2200 LST was higher than that of 1400 LST thepollution could be more serious at 2200 LST with the samepoint source For example in the P1 point source experimentthe polluted area with concentration higher than 01 ppmwassmaller at night (Figures 8(a) and 8(c)) which reflected thatthe diffusion ability was weaker at that moment and morepollutants were trapped in the vortex on the leeward side ofbuilding-A

For the P2 point source experiment as the wind speedincreased the shape of pollution plume was changed a littleand at the height of 25m more pollutants were transportedalong the channel formed by the buildings located on thenorth of P2 Unlike P1 placing on the leeward side building

the P2 point source was set up in a more open area the pollu-tion of P2 was dominated by the convection process ratherthan the turbulent diffusion process Therefore comparingto the daytime unstable situation as wind speed increasedthe convection of the pollutants strengthened and then thepollution was relaxed a little at night (Figures 8(b) and 8(d))

In short it was found that buildings may alter the flowand concentration fields significantly The position of thepoint source had significant influences on the concentrationpattern Comparing the flow and dispersion pattern at twomoments it was found that the convection and turbulentdiffusion were the two important processes to determinethe pollution serious level Within the nocturnal stableatmospheric boundary structure although the ambient windspeed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

10 Advances in Meteorology

42 Simulation Results in Summer

421 Simulation of WRF Summer Experiment Figure 3(b)showed the observed sea level pressure field at 0800 LST 13August 2012 Similar to the winter case the Shenyang areawas under the control of this high pressure system with weaksynoptic system

Figures 4(c) and 4(d) exhibited the diurnal variationsof the observed and simulated 2-m temperature and 10-mwind speed to examine the WRF output The simulatedtemperature was a little lower than observed one at nightand the temperature during the daytime was simulated wellDespite the fact that the simulated wind speed was slightlyhigher the diurnal variation of the wind speed was simulatedwell On the whole the simulation result in summer wasbetter than that in winter

The 10-m wind vector fields and 2-m temperature fieldsof the innermost WRF domain on 16th of February 2012were shown in Figure 9 At 0200 LST the main directionof the wind was northeast while the wind turned to northat 0600 LST The wind speed increased as the land surfacewas heated by the sun It was noted that at 1800 LST thewind direction within the built-up areas of Shenyang wasdifferent from that in the suburb area the wind in the built-up areas was northwestern while the wind in the suburb areawas northern At 2200 LST the wind turned to north in thesimulation region We can also obviously find the urban heatisland effect in Shenyang at 0200 LST 1800 LST and 2200 LSTthe 2-m temperature over the built-up area was significantlyhigher than that of the suburb area

The potential temperature profile height-time section ofthe potential temperature profile and time series of boundarylayer height simulated by WRF were given in Figure 6 Thesurface-based inversion formed at 0400 LST and the intensityof inversion below the height of 500m was 23 K per 100mheight which was stronger than the inversion that happenedin winter at the same time and the depth of the inversionlayer was also thicker than that of winter (Figures 6(a) and6(b)) At 0800 LST since the ground was warmed by thesunlight a thin mixed layer was generated near ground andthe temperature inversion was detached from the ground atthe height of 250m After 0800 LST the low-level inversionlayer disappeared gradually at 1200 LST a mixed layer wasformed in the lower atmosphere from ground to the heightof 700m (Figure 6(b)) In the afternoon the mixed layerextended well to 15 km height (Figure 6(d)) favoring thevertical dilution of pollutant At night the ground was cooledby the nocturnal radiation causing the generation of theinversion stable layer near the ground Comparing to thenocturnal stable layer of the winter case the boundary layerheight of the summer experiment was lower from 0000 LSTto 0600 LST because of the calm ambient wind background(Figures 6(c) and 6(d))

422 Simulation of CFD Experiments in Summer Similarto the winter CFD numerical experiments two experi-ments with different atmospheric boundary structures weredesigned at 1400 LST (unstable case) and 2200 LST (stablecase)

Figure 10 illustrated the simulated concentration (ppm)and wind vector fields at different height at 1400 LST on 13thof August when the ambient wind direction was north Itwas noted that two counterclockwise vortices formed behindbuilding-A which was a typical double-eddy circulationreported by Hunter et al [44] and Zhang et al [45] Compar-ing to the wind vector field at 119911 = 25m the wind vector fieldof 225mwasmuch simpler and the north flowwas dominantin most of the region

At the lower level the distributions of pollutant concen-tration were consistent with the flow patternWhen the pointsourcewas located at P1 or P2 the pollutantswere transportedand trapped in the circulations of the two vortexes behindbuilding-A

Comparing the concentration fields of point sourcesP1 and P2 at two heights it was interesting to find thatthe concentration within the red rectangle in Figure 10 washigher at the height of 225m than the lower level (25mheight) The phenomenon can be explained by the windfields at different height At the height of 25m since redrectangle region was surrounded by buildings where thewind fields were detached from the ambient boundary windand were dominant by the east wind therefore the pollutantreleased from the northern P1 and P2 point sources cannotbe transported to this region directly In the contrary at theheight of 225m the red rectangle regionwas dominant by thenorth wind therefore the pollutant can be easily transportedthere

At 2200 LST when the south ambient wind blew a quitedifferent flow pattern was presented within the built-up area(Figure 11) compared to that of 1400 LST A strong divergencezone can be found in the south of building-A at the heightof 25m indicated by the red dashed rectangle in Figure 11When the airflowblew from the south a typical step-up notchwas formed by building-A (81m) and building-B (24m) asthe vertical wind field presented in Figure 12 the south inletwind was blocked by the taller building (building-A) anddescended along the windward wall of building-A and thendiverged near the ground

At the lower level the wind field around the point sources(P1 and P2) was totally rearranged by the effects of thebuildings around At the height of 225m since the sparserbuilding distribution the wind field was more close to theambient wind Therefore the wind fields of the height of25m and 225m were quite different as well as the pollutantdistributions At 119911 = 25m most of the pollutant releasedfrom P1 and P2 source was transported to south by thedivergence zone formed on the south side building-A

In these two cases it was found that the change of theambient wind direction can significantly affect the flow fieldsand pollutant distributions within the building cluster

5 Discussion and Conclusions

This study examined urban airflow and dispersion patternof pollutant released from hypothetical sources in North-eastern University of Shenyang China by using a WRF-CFD coupled model Two WRF numerical experiments

Advances in Meteorology 11

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(a)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(b)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(c)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(d)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(e)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(f)

Figure 9 The 10-m wind vector fields and 2-m temperature fields of Shenyang on 13th of August 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

12 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

(c)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

01

05

1

25

5

10

20

35

50

(d)

Figure 10 Simulated concentration (ppm) and wind vector fields at 1400 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

(Summer-Run and Winter-Run) were performed to studythe typical features of the atmospheric boundary layer struc-tures of different season Then the coupled WRF-CFD wasused to study how the atmospheric boundary structureambient wind and source position affect the wind fieldand pollutant distribution within the built-up areas It wasfound that the pollutant dispersion pattern and the pollutiondegree dispersion were complicated in the presence of realbuilding clusters and under varying atmospheric bound-ary structures ambient wind and locations of pollutionsources

From this preliminary numerical study it was found thatthe atmospheric boundary structure played a crucial role onthe pollution within the building cluster which determinedthe potential turbulent diffusion ability of the atmosphericsurface layer For example within a nocturnal stable atmo-spheric boundary condition although the ambient wind

speed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

The change of the ambient wind direction can signifi-cantly affect the dispersion pattern of pollutants which was amore sensitive factor than the ambient wind speedThereforewhen a building cluster was designed it was important toconsider the frequency of the ambient wind direction there

Under a given atmospheric state the location of thepollution source would dramatically determine the pollutionpatterns within the built-up areasWhen the pollutant sourcewas set up on the leeward side of the building the pollutantdispersion pattern was dominated by turbulent diffusion pro-cess which was affected by atmospheric boundary structureswhile the convection process dominated when the pollutantsource was set up in a more open area Besides that thedistribution of pollutant concentrationwas driven by the flowpattern

Advances in Meteorology 13

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

A

B

3

Reference vector

A

B

(a)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

B

(b)

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

A

(c)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

(d)

Figure 11 Simulated concentration (ppm) and wind vector fields at 2200 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

A

B

90

60

30

0

Z(m

)

Y (m)6005004003002001000

Reference vector3

Figure 12 The vertical plane of the wind vector field across 119883 =325m

Finally it should be noted that the wind fields anddispersion patterns within the building clusters were com-plicated which cannot be obtained from the ambient wind

TheWRF-CFD numerical evaluation can be used as a reliablemethod to understand the complicated flow and dispersionwithin the built-up areas

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is supported by the China Meteorological Admin-istration Special Public Welfare Research Fund under Grantno GYHY201106033 and the National Natural Science Foun-dation of China under Grant no 41175004

14 Advances in Meteorology

References

[1] H R Olesen R Berkowicz M Ketzel and P Loslashfstroslashm ldquoVal-idation of OML AERMODPRIME and MISKAM using theThompson wind-tunnel dataset for simple stack-building con-figurationsrdquo Boundary-LayerMeteorology vol 131 no 1 pp 73ndash83 2009

[2] R S Thompson ldquoBuilding amplification factors for sourcesnear buildings a wind-tunnel studyrdquo Atmospheric EnvironmentPart A General Topics vol 27 no 15 pp 2313ndash2325 1993

[3] A F Stein and B M Toselli ldquoStreet level air pollution in Cor-doba City ArgentinardquoAtmospheric Environment vol 30 no 20pp 3491ndash3495 1996

[4] RWMacDonald R F Griffiths and S C Cheah ldquoField exper-iments of dispersion through regular arrays of cubic structuresrdquoAtmospheric Environment vol 31 no 6 pp 783ndash795 1997

[5] R W Macdonald R F Griffiths and D J Hall ldquoA comparisonof results from scaled field and wind tunnel modelling ofdispersion in arrays of obstaclesrdquoAtmospheric Environment vol32 no 22 pp 3845ndash3862 1998

[6] M Pavageau andM Schatzmann ldquoWind tunnel measurementsof concentration fluctuations in an urban street canyonrdquo Atmo-spheric Environment vol 33 no 24-25 pp 3961ndash3971 1999

[7] P Kastner-Klein and E J Plate ldquoWind-tunnel study of concen-tration fields in street canyonsrdquo Atmospheric Environment vol33 no 24-25 pp 3973ndash3979 1999

[8] I Mavroidis R F Griffiths and D J Hall ldquoField and windtunnel investigations of plume dispersion around single surfaceobstaclesrdquo Atmospheric Environment vol 37 no 21 pp 2903ndash2918 2003

[9] DDelaunay D Lakehal C Barre andC Sacre ldquoNumerical andwind tunnel simulation of gas dispersion around a rectangularbuildingrdquo Journal ofWind Engineeringamp Industrial Aerodynam-ics vol 67-68 pp 721ndash732 1997

[10] I R Cowan I P Castro and A G Robins ldquoNumericalconsiderations for simulations of flow and dispersion aroundbuildingsrdquo Journal of Wind Engineering and Industrial Aerody-namics vol 67-68 pp 535ndash545 1997

[11] J J Baik and J J Kim ldquoOn the escape of pollutants from urbanstreet canyonsrdquo Atmospheric Environment vol 36 no 3 pp527ndash536 2002

[12] K Nazridoust and G Ahmadi ldquoAirflow and pollutant transportin street canyonsrdquo Journal of Wind Engineering and IndustrialAerodynamics vol 94 no 6 pp 491ndash522 2006

[13] Y Tominaga SMurakami andAMochida ldquoCFDprediction ofgaseous diffusion around a cubic model using a dynamic mixedSGSmodel based on composite grid techniquerdquo Journal ofWindEngineering and Industrial Aerodynamics vol 67-68 pp 827ndash841 1997

[14] K Sada and A Sato ldquoNumerical calculation of flow andstack-gas concentration fluctuation around a cubical buildingrdquoAtmospheric Environment vol 36 no 35 pp 5527ndash5534 2002

[15] X-X Li C-H Liu and D Y C Leung ldquoLarge-eddy simulationof flow and pollutant dispersion in high-aspect-ratio urbanstreet canyons with wall modelrdquo Boundary-Layer Meteorologyvol 129 no 2 pp 249ndash268 2008

[16] M Tewari H Kusaka F Chen et al ldquoImpact of couplinga microscale computational fluid dynamics model with amesoscale model on urban scale contaminant transport anddispersionrdquo Atmospheric Research vol 96 no 4 pp 656ndash6642010

[17] Y S Liu S G Miao C L Zhang G X Cui and Z S ZhangldquoStudy on micro-atmospheric environment by coupling largeeddy simulation with mesoscale modelrdquo Journal of Wind Engi-neering amp Industrial Aerodynamics vol 107-108 pp 106ndash1172012

[18] Y Miao S Liu B Chen B Zhang S Wang and S Li ldquoSimu-lating urban flow and dispersion in Beijing by coupling a CFDmodel with theWRFmodelrdquoAdvances in Atmospheric Sciencesvol 30 no 6 pp 1663ndash1678 2013

[19] X Fang W Jiang S Miao et al ldquoThe multi-scale numericalmodeling system for research on the relationship betweenurban planning and meteorological environmentrdquo Advances inAtmospheric Sciences vol 21 no 1 pp 103ndash112 2004

[20] Y C Miao S H Liu H Zheng et al ldquoA multi-scale urbanatmospheric dispersion model for emergency managementrdquoAdvances in Atmospheric Sciences vol 31 no 6 pp 1353ndash13652014

[21] S Miao W Jiang X Wang and W Guo ldquoImpact assessmentof urban meteorology and the atmospheric environment usingurban sub-domain planningrdquoBoundary-LayerMeteorology vol118 no 1 pp 133ndash150 2006

[22] OpenCFD OpenFOAM The Open Source Computational FluidDynamics (CFD) Toolbox 2008 httpwwwopencfdcoukopenfoam

[23] J H Ferziger and M Peric Computational Methods for FluidDynamics Springer Berlin Germany 3rd edition 2001

[24] Z I Janjic ldquoThe step-mountain coordinate physical packagerdquoMonthly Weather Review vol 118 no 7 pp 1429ndash1443 1990

[25] Z I Janjic ldquoThe step-mountain eta coordinate model furtherdevelopments of the convection viscous sublayer and turbu-lence closure schemesrdquoMonthlyWeather Review vol 122 no 5pp 927ndash945 1994

[26] E J Mlawer S J Taubman P D Brown M J Iacono and S AClough ldquoRadiative transfer for inhomogeneous atmospheresRRTM a validated correlated-k model for the longwaverdquoJournal of Geophysical Research Atmospheres vol 102 no 14pp 16663ndash16682 1997

[27] J Dudhia ldquoNumerical study of convection observed dur-ing the winter monsoon experiment using a mesoscale two-dimensionalmodelrdquo Journal of theAtmospheric Sciences vol 46no 20 pp 3077ndash3107 1989

[28] S-Y Hong J Dudhia and S-H Chen ldquoA revised approach toice microphysical processes for the bulk parameterization ofclouds and precipitationrdquoMonthlyWeather Review vol 132 no1 pp 103ndash120 2004

[29] J S Kain ldquoThe Kain Fritsch convective parameterization anupdaterdquo Journal of Applied Meteorology vol 43 no 1 pp 170ndash181 2004

[30] F Chen and J Dudhia ldquoCoupling and advanced land surface-hydrology model with the Penn State-NCAR MM5 modelingsystem Part I model implementation and sensitivityrdquoMonthlyWeather Review vol 129 no 4 pp 569ndash585 2001

[31] H Kusaka H Kondo Y Kikegawa and F Kimura ldquoA simplesingle-layer urban canopy model for atmospheric modelscomparison with multi-layer and slab modelsrdquo Boundary-LayerMeteorology vol 101 no 3 pp 329ndash358 2001

[32] H Kusaka and F Kimura ldquoCoupling a single-layer urbancanopy model with a simple atmospheric model impact onurban heat island simulation for an idealized caserdquo Journal of theMeteorological Society of Japan vol 82 no 1 pp 67ndash80 2004

Advances in Meteorology 15

[33] B Grisogono and J Oerlemans ldquoJustifying the WKB approxi-mation in pure katabatic flowsrdquo Tellus A Dynamic Meteorologyand Oceanography vol 54 no 5 pp 453ndash462 2002

[34] A Jericevic L Kraljevic B Grisogono H Fagerli and Z Vece-naj ldquoParameterization of vertical diffusion and the atmosphericboundary layer height determination in the EMEP modelrdquoAtmospheric Chemistry and Physics vol 10 no 2 pp 341ndash3642010

[35] C Bicheng L ShuhuaM Yucong et al ldquoConstruction and vali-dation of a computational fluid dynamics approach for flow anddispersion modeling in urban areardquo Journal of MeteorologicalResearch vol 27 no 6 pp 923ndash941 2013

[36] C Liqiang and Y Hongbin ldquoSynoptic patterns of regional airpollution in Liaoning Provincerdquo Environmental Pollution ampControl vol 28 no 6 pp 435ndash451 2006 (Chinese)

[37] S A Adachi H KusakaM G Duda et al ldquoImprovement of thesingle-layer UCM in the WRF modelrdquo in Proceedings of the 8thInternational Conference on Urban Climates (ICUC8 rsquo12) 2012

[38] G Roux Y Liu L D Monache et al ldquoVerification of highresolution WRF-RTFDDA surface forecasts over mountainsand plainsrdquo Proceedings of the 10th WRF Usersrsquo Workshop pp20ndash23 2009

[39] S Shimada T Ohsawa S Chikaoka et al ldquoAccuracy of the windspeed profile in the lower PBL as simulated by theWRFmodelrdquoSola vol 7 pp 109ndash112 2011

[40] P A Jimenez and J Dudhia ldquoImproving the representation ofresolved and unresolved topographic effects on surface wind inthe wrf modelrdquo Journal of AppliedMeteorology and Climatologyvol 51 no 2 pp 300ndash316 2012

[41] Z I Janjic ldquoNonsingular implementation of theMellor-Yamadalevel 25 scheme in the NCEP Meso modelrdquo NOAANWSNCEP Office Note 437 2001

[42] X-M Hu J W Nielsen-Gammon and F Zhang ldquoEvaluationof three planetary boundary layer schemes in the WRF modelrdquoJournal of Applied Meteorology and Climatology vol 49 no 9pp 1831ndash1844 2010

[43] J W Nielsen-Gammon C L Powell M J Mahoney et alldquoMultisensor estimation of mixing heights over a coastal cityrdquoJournal of Applied Meteorology and Climatology vol 47 no 1pp 27ndash43 2008

[44] L J Hunter G T Johnson and I D Watson ldquoAn investigationof three-dimensional characteristics of flow regimes withinthe urban canyonrdquo Atmospheric Environment Part B UrbanAtmosphere vol 26 no 4 pp 425ndash432 1992

[45] Y Q Zhang S P Arya and W H Snyder ldquoA comparisonof numerical and physical modeling of stable atmosphericflow and dispersion around a cubical buildingrdquo AtmosphericEnvironment vol 30 no 8 pp 1327ndash1345 1996

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

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MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

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Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

Advances in Meteorology 9

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

(c)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(d)

Figure 8 Simulated concentration (ppm) and wind vector fields at 2200 LST on 16th of February (a b) at 119911 = 25m (c d) at 119911 = 225m (ac) the point source was located at P1 (b d) the point source was located at P2

At 2200 LST a typical nocturnal stable layer was formednear the surface (Figure 6(e)) which may inhibit the dis-persion process of pollutants Although the ambient windspeed of 2200 LST was higher than that of 1400 LST thepollution could be more serious at 2200 LST with the samepoint source For example in the P1 point source experimentthe polluted area with concentration higher than 01 ppmwassmaller at night (Figures 8(a) and 8(c)) which reflected thatthe diffusion ability was weaker at that moment and morepollutants were trapped in the vortex on the leeward side ofbuilding-A

For the P2 point source experiment as the wind speedincreased the shape of pollution plume was changed a littleand at the height of 25m more pollutants were transportedalong the channel formed by the buildings located on thenorth of P2 Unlike P1 placing on the leeward side building

the P2 point source was set up in a more open area the pollu-tion of P2 was dominated by the convection process ratherthan the turbulent diffusion process Therefore comparingto the daytime unstable situation as wind speed increasedthe convection of the pollutants strengthened and then thepollution was relaxed a little at night (Figures 8(b) and 8(d))

In short it was found that buildings may alter the flowand concentration fields significantly The position of thepoint source had significant influences on the concentrationpattern Comparing the flow and dispersion pattern at twomoments it was found that the convection and turbulentdiffusion were the two important processes to determinethe pollution serious level Within the nocturnal stableatmospheric boundary structure although the ambient windspeed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

10 Advances in Meteorology

42 Simulation Results in Summer

421 Simulation of WRF Summer Experiment Figure 3(b)showed the observed sea level pressure field at 0800 LST 13August 2012 Similar to the winter case the Shenyang areawas under the control of this high pressure system with weaksynoptic system

Figures 4(c) and 4(d) exhibited the diurnal variationsof the observed and simulated 2-m temperature and 10-mwind speed to examine the WRF output The simulatedtemperature was a little lower than observed one at nightand the temperature during the daytime was simulated wellDespite the fact that the simulated wind speed was slightlyhigher the diurnal variation of the wind speed was simulatedwell On the whole the simulation result in summer wasbetter than that in winter

The 10-m wind vector fields and 2-m temperature fieldsof the innermost WRF domain on 16th of February 2012were shown in Figure 9 At 0200 LST the main directionof the wind was northeast while the wind turned to northat 0600 LST The wind speed increased as the land surfacewas heated by the sun It was noted that at 1800 LST thewind direction within the built-up areas of Shenyang wasdifferent from that in the suburb area the wind in the built-up areas was northwestern while the wind in the suburb areawas northern At 2200 LST the wind turned to north in thesimulation region We can also obviously find the urban heatisland effect in Shenyang at 0200 LST 1800 LST and 2200 LSTthe 2-m temperature over the built-up area was significantlyhigher than that of the suburb area

The potential temperature profile height-time section ofthe potential temperature profile and time series of boundarylayer height simulated by WRF were given in Figure 6 Thesurface-based inversion formed at 0400 LST and the intensityof inversion below the height of 500m was 23 K per 100mheight which was stronger than the inversion that happenedin winter at the same time and the depth of the inversionlayer was also thicker than that of winter (Figures 6(a) and6(b)) At 0800 LST since the ground was warmed by thesunlight a thin mixed layer was generated near ground andthe temperature inversion was detached from the ground atthe height of 250m After 0800 LST the low-level inversionlayer disappeared gradually at 1200 LST a mixed layer wasformed in the lower atmosphere from ground to the heightof 700m (Figure 6(b)) In the afternoon the mixed layerextended well to 15 km height (Figure 6(d)) favoring thevertical dilution of pollutant At night the ground was cooledby the nocturnal radiation causing the generation of theinversion stable layer near the ground Comparing to thenocturnal stable layer of the winter case the boundary layerheight of the summer experiment was lower from 0000 LSTto 0600 LST because of the calm ambient wind background(Figures 6(c) and 6(d))

422 Simulation of CFD Experiments in Summer Similarto the winter CFD numerical experiments two experi-ments with different atmospheric boundary structures weredesigned at 1400 LST (unstable case) and 2200 LST (stablecase)

Figure 10 illustrated the simulated concentration (ppm)and wind vector fields at different height at 1400 LST on 13thof August when the ambient wind direction was north Itwas noted that two counterclockwise vortices formed behindbuilding-A which was a typical double-eddy circulationreported by Hunter et al [44] and Zhang et al [45] Compar-ing to the wind vector field at 119911 = 25m the wind vector fieldof 225mwasmuch simpler and the north flowwas dominantin most of the region

At the lower level the distributions of pollutant concen-tration were consistent with the flow patternWhen the pointsourcewas located at P1 or P2 the pollutantswere transportedand trapped in the circulations of the two vortexes behindbuilding-A

Comparing the concentration fields of point sourcesP1 and P2 at two heights it was interesting to find thatthe concentration within the red rectangle in Figure 10 washigher at the height of 225m than the lower level (25mheight) The phenomenon can be explained by the windfields at different height At the height of 25m since redrectangle region was surrounded by buildings where thewind fields were detached from the ambient boundary windand were dominant by the east wind therefore the pollutantreleased from the northern P1 and P2 point sources cannotbe transported to this region directly In the contrary at theheight of 225m the red rectangle regionwas dominant by thenorth wind therefore the pollutant can be easily transportedthere

At 2200 LST when the south ambient wind blew a quitedifferent flow pattern was presented within the built-up area(Figure 11) compared to that of 1400 LST A strong divergencezone can be found in the south of building-A at the heightof 25m indicated by the red dashed rectangle in Figure 11When the airflowblew from the south a typical step-up notchwas formed by building-A (81m) and building-B (24m) asthe vertical wind field presented in Figure 12 the south inletwind was blocked by the taller building (building-A) anddescended along the windward wall of building-A and thendiverged near the ground

At the lower level the wind field around the point sources(P1 and P2) was totally rearranged by the effects of thebuildings around At the height of 225m since the sparserbuilding distribution the wind field was more close to theambient wind Therefore the wind fields of the height of25m and 225m were quite different as well as the pollutantdistributions At 119911 = 25m most of the pollutant releasedfrom P1 and P2 source was transported to south by thedivergence zone formed on the south side building-A

In these two cases it was found that the change of theambient wind direction can significantly affect the flow fieldsand pollutant distributions within the building cluster

5 Discussion and Conclusions

This study examined urban airflow and dispersion patternof pollutant released from hypothetical sources in North-eastern University of Shenyang China by using a WRF-CFD coupled model Two WRF numerical experiments

Advances in Meteorology 11

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(a)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(b)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(c)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(d)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(e)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(f)

Figure 9 The 10-m wind vector fields and 2-m temperature fields of Shenyang on 13th of August 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

12 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

(c)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

01

05

1

25

5

10

20

35

50

(d)

Figure 10 Simulated concentration (ppm) and wind vector fields at 1400 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

(Summer-Run and Winter-Run) were performed to studythe typical features of the atmospheric boundary layer struc-tures of different season Then the coupled WRF-CFD wasused to study how the atmospheric boundary structureambient wind and source position affect the wind fieldand pollutant distribution within the built-up areas It wasfound that the pollutant dispersion pattern and the pollutiondegree dispersion were complicated in the presence of realbuilding clusters and under varying atmospheric bound-ary structures ambient wind and locations of pollutionsources

From this preliminary numerical study it was found thatthe atmospheric boundary structure played a crucial role onthe pollution within the building cluster which determinedthe potential turbulent diffusion ability of the atmosphericsurface layer For example within a nocturnal stable atmo-spheric boundary condition although the ambient wind

speed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

The change of the ambient wind direction can signifi-cantly affect the dispersion pattern of pollutants which was amore sensitive factor than the ambient wind speedThereforewhen a building cluster was designed it was important toconsider the frequency of the ambient wind direction there

Under a given atmospheric state the location of thepollution source would dramatically determine the pollutionpatterns within the built-up areasWhen the pollutant sourcewas set up on the leeward side of the building the pollutantdispersion pattern was dominated by turbulent diffusion pro-cess which was affected by atmospheric boundary structureswhile the convection process dominated when the pollutantsource was set up in a more open area Besides that thedistribution of pollutant concentrationwas driven by the flowpattern

Advances in Meteorology 13

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

A

B

3

Reference vector

A

B

(a)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

B

(b)

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

A

(c)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

(d)

Figure 11 Simulated concentration (ppm) and wind vector fields at 2200 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

A

B

90

60

30

0

Z(m

)

Y (m)6005004003002001000

Reference vector3

Figure 12 The vertical plane of the wind vector field across 119883 =325m

Finally it should be noted that the wind fields anddispersion patterns within the building clusters were com-plicated which cannot be obtained from the ambient wind

TheWRF-CFD numerical evaluation can be used as a reliablemethod to understand the complicated flow and dispersionwithin the built-up areas

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is supported by the China Meteorological Admin-istration Special Public Welfare Research Fund under Grantno GYHY201106033 and the National Natural Science Foun-dation of China under Grant no 41175004

14 Advances in Meteorology

References

[1] H R Olesen R Berkowicz M Ketzel and P Loslashfstroslashm ldquoVal-idation of OML AERMODPRIME and MISKAM using theThompson wind-tunnel dataset for simple stack-building con-figurationsrdquo Boundary-LayerMeteorology vol 131 no 1 pp 73ndash83 2009

[2] R S Thompson ldquoBuilding amplification factors for sourcesnear buildings a wind-tunnel studyrdquo Atmospheric EnvironmentPart A General Topics vol 27 no 15 pp 2313ndash2325 1993

[3] A F Stein and B M Toselli ldquoStreet level air pollution in Cor-doba City ArgentinardquoAtmospheric Environment vol 30 no 20pp 3491ndash3495 1996

[4] RWMacDonald R F Griffiths and S C Cheah ldquoField exper-iments of dispersion through regular arrays of cubic structuresrdquoAtmospheric Environment vol 31 no 6 pp 783ndash795 1997

[5] R W Macdonald R F Griffiths and D J Hall ldquoA comparisonof results from scaled field and wind tunnel modelling ofdispersion in arrays of obstaclesrdquoAtmospheric Environment vol32 no 22 pp 3845ndash3862 1998

[6] M Pavageau andM Schatzmann ldquoWind tunnel measurementsof concentration fluctuations in an urban street canyonrdquo Atmo-spheric Environment vol 33 no 24-25 pp 3961ndash3971 1999

[7] P Kastner-Klein and E J Plate ldquoWind-tunnel study of concen-tration fields in street canyonsrdquo Atmospheric Environment vol33 no 24-25 pp 3973ndash3979 1999

[8] I Mavroidis R F Griffiths and D J Hall ldquoField and windtunnel investigations of plume dispersion around single surfaceobstaclesrdquo Atmospheric Environment vol 37 no 21 pp 2903ndash2918 2003

[9] DDelaunay D Lakehal C Barre andC Sacre ldquoNumerical andwind tunnel simulation of gas dispersion around a rectangularbuildingrdquo Journal ofWind Engineeringamp Industrial Aerodynam-ics vol 67-68 pp 721ndash732 1997

[10] I R Cowan I P Castro and A G Robins ldquoNumericalconsiderations for simulations of flow and dispersion aroundbuildingsrdquo Journal of Wind Engineering and Industrial Aerody-namics vol 67-68 pp 535ndash545 1997

[11] J J Baik and J J Kim ldquoOn the escape of pollutants from urbanstreet canyonsrdquo Atmospheric Environment vol 36 no 3 pp527ndash536 2002

[12] K Nazridoust and G Ahmadi ldquoAirflow and pollutant transportin street canyonsrdquo Journal of Wind Engineering and IndustrialAerodynamics vol 94 no 6 pp 491ndash522 2006

[13] Y Tominaga SMurakami andAMochida ldquoCFDprediction ofgaseous diffusion around a cubic model using a dynamic mixedSGSmodel based on composite grid techniquerdquo Journal ofWindEngineering and Industrial Aerodynamics vol 67-68 pp 827ndash841 1997

[14] K Sada and A Sato ldquoNumerical calculation of flow andstack-gas concentration fluctuation around a cubical buildingrdquoAtmospheric Environment vol 36 no 35 pp 5527ndash5534 2002

[15] X-X Li C-H Liu and D Y C Leung ldquoLarge-eddy simulationof flow and pollutant dispersion in high-aspect-ratio urbanstreet canyons with wall modelrdquo Boundary-Layer Meteorologyvol 129 no 2 pp 249ndash268 2008

[16] M Tewari H Kusaka F Chen et al ldquoImpact of couplinga microscale computational fluid dynamics model with amesoscale model on urban scale contaminant transport anddispersionrdquo Atmospheric Research vol 96 no 4 pp 656ndash6642010

[17] Y S Liu S G Miao C L Zhang G X Cui and Z S ZhangldquoStudy on micro-atmospheric environment by coupling largeeddy simulation with mesoscale modelrdquo Journal of Wind Engi-neering amp Industrial Aerodynamics vol 107-108 pp 106ndash1172012

[18] Y Miao S Liu B Chen B Zhang S Wang and S Li ldquoSimu-lating urban flow and dispersion in Beijing by coupling a CFDmodel with theWRFmodelrdquoAdvances in Atmospheric Sciencesvol 30 no 6 pp 1663ndash1678 2013

[19] X Fang W Jiang S Miao et al ldquoThe multi-scale numericalmodeling system for research on the relationship betweenurban planning and meteorological environmentrdquo Advances inAtmospheric Sciences vol 21 no 1 pp 103ndash112 2004

[20] Y C Miao S H Liu H Zheng et al ldquoA multi-scale urbanatmospheric dispersion model for emergency managementrdquoAdvances in Atmospheric Sciences vol 31 no 6 pp 1353ndash13652014

[21] S Miao W Jiang X Wang and W Guo ldquoImpact assessmentof urban meteorology and the atmospheric environment usingurban sub-domain planningrdquoBoundary-LayerMeteorology vol118 no 1 pp 133ndash150 2006

[22] OpenCFD OpenFOAM The Open Source Computational FluidDynamics (CFD) Toolbox 2008 httpwwwopencfdcoukopenfoam

[23] J H Ferziger and M Peric Computational Methods for FluidDynamics Springer Berlin Germany 3rd edition 2001

[24] Z I Janjic ldquoThe step-mountain coordinate physical packagerdquoMonthly Weather Review vol 118 no 7 pp 1429ndash1443 1990

[25] Z I Janjic ldquoThe step-mountain eta coordinate model furtherdevelopments of the convection viscous sublayer and turbu-lence closure schemesrdquoMonthlyWeather Review vol 122 no 5pp 927ndash945 1994

[26] E J Mlawer S J Taubman P D Brown M J Iacono and S AClough ldquoRadiative transfer for inhomogeneous atmospheresRRTM a validated correlated-k model for the longwaverdquoJournal of Geophysical Research Atmospheres vol 102 no 14pp 16663ndash16682 1997

[27] J Dudhia ldquoNumerical study of convection observed dur-ing the winter monsoon experiment using a mesoscale two-dimensionalmodelrdquo Journal of theAtmospheric Sciences vol 46no 20 pp 3077ndash3107 1989

[28] S-Y Hong J Dudhia and S-H Chen ldquoA revised approach toice microphysical processes for the bulk parameterization ofclouds and precipitationrdquoMonthlyWeather Review vol 132 no1 pp 103ndash120 2004

[29] J S Kain ldquoThe Kain Fritsch convective parameterization anupdaterdquo Journal of Applied Meteorology vol 43 no 1 pp 170ndash181 2004

[30] F Chen and J Dudhia ldquoCoupling and advanced land surface-hydrology model with the Penn State-NCAR MM5 modelingsystem Part I model implementation and sensitivityrdquoMonthlyWeather Review vol 129 no 4 pp 569ndash585 2001

[31] H Kusaka H Kondo Y Kikegawa and F Kimura ldquoA simplesingle-layer urban canopy model for atmospheric modelscomparison with multi-layer and slab modelsrdquo Boundary-LayerMeteorology vol 101 no 3 pp 329ndash358 2001

[32] H Kusaka and F Kimura ldquoCoupling a single-layer urbancanopy model with a simple atmospheric model impact onurban heat island simulation for an idealized caserdquo Journal of theMeteorological Society of Japan vol 82 no 1 pp 67ndash80 2004

Advances in Meteorology 15

[33] B Grisogono and J Oerlemans ldquoJustifying the WKB approxi-mation in pure katabatic flowsrdquo Tellus A Dynamic Meteorologyand Oceanography vol 54 no 5 pp 453ndash462 2002

[34] A Jericevic L Kraljevic B Grisogono H Fagerli and Z Vece-naj ldquoParameterization of vertical diffusion and the atmosphericboundary layer height determination in the EMEP modelrdquoAtmospheric Chemistry and Physics vol 10 no 2 pp 341ndash3642010

[35] C Bicheng L ShuhuaM Yucong et al ldquoConstruction and vali-dation of a computational fluid dynamics approach for flow anddispersion modeling in urban areardquo Journal of MeteorologicalResearch vol 27 no 6 pp 923ndash941 2013

[36] C Liqiang and Y Hongbin ldquoSynoptic patterns of regional airpollution in Liaoning Provincerdquo Environmental Pollution ampControl vol 28 no 6 pp 435ndash451 2006 (Chinese)

[37] S A Adachi H KusakaM G Duda et al ldquoImprovement of thesingle-layer UCM in the WRF modelrdquo in Proceedings of the 8thInternational Conference on Urban Climates (ICUC8 rsquo12) 2012

[38] G Roux Y Liu L D Monache et al ldquoVerification of highresolution WRF-RTFDDA surface forecasts over mountainsand plainsrdquo Proceedings of the 10th WRF Usersrsquo Workshop pp20ndash23 2009

[39] S Shimada T Ohsawa S Chikaoka et al ldquoAccuracy of the windspeed profile in the lower PBL as simulated by theWRFmodelrdquoSola vol 7 pp 109ndash112 2011

[40] P A Jimenez and J Dudhia ldquoImproving the representation ofresolved and unresolved topographic effects on surface wind inthe wrf modelrdquo Journal of AppliedMeteorology and Climatologyvol 51 no 2 pp 300ndash316 2012

[41] Z I Janjic ldquoNonsingular implementation of theMellor-Yamadalevel 25 scheme in the NCEP Meso modelrdquo NOAANWSNCEP Office Note 437 2001

[42] X-M Hu J W Nielsen-Gammon and F Zhang ldquoEvaluationof three planetary boundary layer schemes in the WRF modelrdquoJournal of Applied Meteorology and Climatology vol 49 no 9pp 1831ndash1844 2010

[43] J W Nielsen-Gammon C L Powell M J Mahoney et alldquoMultisensor estimation of mixing heights over a coastal cityrdquoJournal of Applied Meteorology and Climatology vol 47 no 1pp 27ndash43 2008

[44] L J Hunter G T Johnson and I D Watson ldquoAn investigationof three-dimensional characteristics of flow regimes withinthe urban canyonrdquo Atmospheric Environment Part B UrbanAtmosphere vol 26 no 4 pp 425ndash432 1992

[45] Y Q Zhang S P Arya and W H Snyder ldquoA comparisonof numerical and physical modeling of stable atmosphericflow and dispersion around a cubical buildingrdquo AtmosphericEnvironment vol 30 no 8 pp 1327ndash1345 1996

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

10 Advances in Meteorology

42 Simulation Results in Summer

421 Simulation of WRF Summer Experiment Figure 3(b)showed the observed sea level pressure field at 0800 LST 13August 2012 Similar to the winter case the Shenyang areawas under the control of this high pressure system with weaksynoptic system

Figures 4(c) and 4(d) exhibited the diurnal variationsof the observed and simulated 2-m temperature and 10-mwind speed to examine the WRF output The simulatedtemperature was a little lower than observed one at nightand the temperature during the daytime was simulated wellDespite the fact that the simulated wind speed was slightlyhigher the diurnal variation of the wind speed was simulatedwell On the whole the simulation result in summer wasbetter than that in winter

The 10-m wind vector fields and 2-m temperature fieldsof the innermost WRF domain on 16th of February 2012were shown in Figure 9 At 0200 LST the main directionof the wind was northeast while the wind turned to northat 0600 LST The wind speed increased as the land surfacewas heated by the sun It was noted that at 1800 LST thewind direction within the built-up areas of Shenyang wasdifferent from that in the suburb area the wind in the built-up areas was northwestern while the wind in the suburb areawas northern At 2200 LST the wind turned to north in thesimulation region We can also obviously find the urban heatisland effect in Shenyang at 0200 LST 1800 LST and 2200 LSTthe 2-m temperature over the built-up area was significantlyhigher than that of the suburb area

The potential temperature profile height-time section ofthe potential temperature profile and time series of boundarylayer height simulated by WRF were given in Figure 6 Thesurface-based inversion formed at 0400 LST and the intensityof inversion below the height of 500m was 23 K per 100mheight which was stronger than the inversion that happenedin winter at the same time and the depth of the inversionlayer was also thicker than that of winter (Figures 6(a) and6(b)) At 0800 LST since the ground was warmed by thesunlight a thin mixed layer was generated near ground andthe temperature inversion was detached from the ground atthe height of 250m After 0800 LST the low-level inversionlayer disappeared gradually at 1200 LST a mixed layer wasformed in the lower atmosphere from ground to the heightof 700m (Figure 6(b)) In the afternoon the mixed layerextended well to 15 km height (Figure 6(d)) favoring thevertical dilution of pollutant At night the ground was cooledby the nocturnal radiation causing the generation of theinversion stable layer near the ground Comparing to thenocturnal stable layer of the winter case the boundary layerheight of the summer experiment was lower from 0000 LSTto 0600 LST because of the calm ambient wind background(Figures 6(c) and 6(d))

422 Simulation of CFD Experiments in Summer Similarto the winter CFD numerical experiments two experi-ments with different atmospheric boundary structures weredesigned at 1400 LST (unstable case) and 2200 LST (stablecase)

Figure 10 illustrated the simulated concentration (ppm)and wind vector fields at different height at 1400 LST on 13thof August when the ambient wind direction was north Itwas noted that two counterclockwise vortices formed behindbuilding-A which was a typical double-eddy circulationreported by Hunter et al [44] and Zhang et al [45] Compar-ing to the wind vector field at 119911 = 25m the wind vector fieldof 225mwasmuch simpler and the north flowwas dominantin most of the region

At the lower level the distributions of pollutant concen-tration were consistent with the flow patternWhen the pointsourcewas located at P1 or P2 the pollutantswere transportedand trapped in the circulations of the two vortexes behindbuilding-A

Comparing the concentration fields of point sourcesP1 and P2 at two heights it was interesting to find thatthe concentration within the red rectangle in Figure 10 washigher at the height of 225m than the lower level (25mheight) The phenomenon can be explained by the windfields at different height At the height of 25m since redrectangle region was surrounded by buildings where thewind fields were detached from the ambient boundary windand were dominant by the east wind therefore the pollutantreleased from the northern P1 and P2 point sources cannotbe transported to this region directly In the contrary at theheight of 225m the red rectangle regionwas dominant by thenorth wind therefore the pollutant can be easily transportedthere

At 2200 LST when the south ambient wind blew a quitedifferent flow pattern was presented within the built-up area(Figure 11) compared to that of 1400 LST A strong divergencezone can be found in the south of building-A at the heightof 25m indicated by the red dashed rectangle in Figure 11When the airflowblew from the south a typical step-up notchwas formed by building-A (81m) and building-B (24m) asthe vertical wind field presented in Figure 12 the south inletwind was blocked by the taller building (building-A) anddescended along the windward wall of building-A and thendiverged near the ground

At the lower level the wind field around the point sources(P1 and P2) was totally rearranged by the effects of thebuildings around At the height of 225m since the sparserbuilding distribution the wind field was more close to theambient wind Therefore the wind fields of the height of25m and 225m were quite different as well as the pollutantdistributions At 119911 = 25m most of the pollutant releasedfrom P1 and P2 source was transported to south by thedivergence zone formed on the south side building-A

In these two cases it was found that the change of theambient wind direction can significantly affect the flow fieldsand pollutant distributions within the building cluster

5 Discussion and Conclusions

This study examined urban airflow and dispersion patternof pollutant released from hypothetical sources in North-eastern University of Shenyang China by using a WRF-CFD coupled model Two WRF numerical experiments

Advances in Meteorology 11

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(a)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(b)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(c)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(d)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(e)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(f)

Figure 9 The 10-m wind vector fields and 2-m temperature fields of Shenyang on 13th of August 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

12 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

(c)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

01

05

1

25

5

10

20

35

50

(d)

Figure 10 Simulated concentration (ppm) and wind vector fields at 1400 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

(Summer-Run and Winter-Run) were performed to studythe typical features of the atmospheric boundary layer struc-tures of different season Then the coupled WRF-CFD wasused to study how the atmospheric boundary structureambient wind and source position affect the wind fieldand pollutant distribution within the built-up areas It wasfound that the pollutant dispersion pattern and the pollutiondegree dispersion were complicated in the presence of realbuilding clusters and under varying atmospheric bound-ary structures ambient wind and locations of pollutionsources

From this preliminary numerical study it was found thatthe atmospheric boundary structure played a crucial role onthe pollution within the building cluster which determinedthe potential turbulent diffusion ability of the atmosphericsurface layer For example within a nocturnal stable atmo-spheric boundary condition although the ambient wind

speed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

The change of the ambient wind direction can signifi-cantly affect the dispersion pattern of pollutants which was amore sensitive factor than the ambient wind speedThereforewhen a building cluster was designed it was important toconsider the frequency of the ambient wind direction there

Under a given atmospheric state the location of thepollution source would dramatically determine the pollutionpatterns within the built-up areasWhen the pollutant sourcewas set up on the leeward side of the building the pollutantdispersion pattern was dominated by turbulent diffusion pro-cess which was affected by atmospheric boundary structureswhile the convection process dominated when the pollutantsource was set up in a more open area Besides that thedistribution of pollutant concentrationwas driven by the flowpattern

Advances in Meteorology 13

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

A

B

3

Reference vector

A

B

(a)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

B

(b)

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

A

(c)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

(d)

Figure 11 Simulated concentration (ppm) and wind vector fields at 2200 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

A

B

90

60

30

0

Z(m

)

Y (m)6005004003002001000

Reference vector3

Figure 12 The vertical plane of the wind vector field across 119883 =325m

Finally it should be noted that the wind fields anddispersion patterns within the building clusters were com-plicated which cannot be obtained from the ambient wind

TheWRF-CFD numerical evaluation can be used as a reliablemethod to understand the complicated flow and dispersionwithin the built-up areas

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is supported by the China Meteorological Admin-istration Special Public Welfare Research Fund under Grantno GYHY201106033 and the National Natural Science Foun-dation of China under Grant no 41175004

14 Advances in Meteorology

References

[1] H R Olesen R Berkowicz M Ketzel and P Loslashfstroslashm ldquoVal-idation of OML AERMODPRIME and MISKAM using theThompson wind-tunnel dataset for simple stack-building con-figurationsrdquo Boundary-LayerMeteorology vol 131 no 1 pp 73ndash83 2009

[2] R S Thompson ldquoBuilding amplification factors for sourcesnear buildings a wind-tunnel studyrdquo Atmospheric EnvironmentPart A General Topics vol 27 no 15 pp 2313ndash2325 1993

[3] A F Stein and B M Toselli ldquoStreet level air pollution in Cor-doba City ArgentinardquoAtmospheric Environment vol 30 no 20pp 3491ndash3495 1996

[4] RWMacDonald R F Griffiths and S C Cheah ldquoField exper-iments of dispersion through regular arrays of cubic structuresrdquoAtmospheric Environment vol 31 no 6 pp 783ndash795 1997

[5] R W Macdonald R F Griffiths and D J Hall ldquoA comparisonof results from scaled field and wind tunnel modelling ofdispersion in arrays of obstaclesrdquoAtmospheric Environment vol32 no 22 pp 3845ndash3862 1998

[6] M Pavageau andM Schatzmann ldquoWind tunnel measurementsof concentration fluctuations in an urban street canyonrdquo Atmo-spheric Environment vol 33 no 24-25 pp 3961ndash3971 1999

[7] P Kastner-Klein and E J Plate ldquoWind-tunnel study of concen-tration fields in street canyonsrdquo Atmospheric Environment vol33 no 24-25 pp 3973ndash3979 1999

[8] I Mavroidis R F Griffiths and D J Hall ldquoField and windtunnel investigations of plume dispersion around single surfaceobstaclesrdquo Atmospheric Environment vol 37 no 21 pp 2903ndash2918 2003

[9] DDelaunay D Lakehal C Barre andC Sacre ldquoNumerical andwind tunnel simulation of gas dispersion around a rectangularbuildingrdquo Journal ofWind Engineeringamp Industrial Aerodynam-ics vol 67-68 pp 721ndash732 1997

[10] I R Cowan I P Castro and A G Robins ldquoNumericalconsiderations for simulations of flow and dispersion aroundbuildingsrdquo Journal of Wind Engineering and Industrial Aerody-namics vol 67-68 pp 535ndash545 1997

[11] J J Baik and J J Kim ldquoOn the escape of pollutants from urbanstreet canyonsrdquo Atmospheric Environment vol 36 no 3 pp527ndash536 2002

[12] K Nazridoust and G Ahmadi ldquoAirflow and pollutant transportin street canyonsrdquo Journal of Wind Engineering and IndustrialAerodynamics vol 94 no 6 pp 491ndash522 2006

[13] Y Tominaga SMurakami andAMochida ldquoCFDprediction ofgaseous diffusion around a cubic model using a dynamic mixedSGSmodel based on composite grid techniquerdquo Journal ofWindEngineering and Industrial Aerodynamics vol 67-68 pp 827ndash841 1997

[14] K Sada and A Sato ldquoNumerical calculation of flow andstack-gas concentration fluctuation around a cubical buildingrdquoAtmospheric Environment vol 36 no 35 pp 5527ndash5534 2002

[15] X-X Li C-H Liu and D Y C Leung ldquoLarge-eddy simulationof flow and pollutant dispersion in high-aspect-ratio urbanstreet canyons with wall modelrdquo Boundary-Layer Meteorologyvol 129 no 2 pp 249ndash268 2008

[16] M Tewari H Kusaka F Chen et al ldquoImpact of couplinga microscale computational fluid dynamics model with amesoscale model on urban scale contaminant transport anddispersionrdquo Atmospheric Research vol 96 no 4 pp 656ndash6642010

[17] Y S Liu S G Miao C L Zhang G X Cui and Z S ZhangldquoStudy on micro-atmospheric environment by coupling largeeddy simulation with mesoscale modelrdquo Journal of Wind Engi-neering amp Industrial Aerodynamics vol 107-108 pp 106ndash1172012

[18] Y Miao S Liu B Chen B Zhang S Wang and S Li ldquoSimu-lating urban flow and dispersion in Beijing by coupling a CFDmodel with theWRFmodelrdquoAdvances in Atmospheric Sciencesvol 30 no 6 pp 1663ndash1678 2013

[19] X Fang W Jiang S Miao et al ldquoThe multi-scale numericalmodeling system for research on the relationship betweenurban planning and meteorological environmentrdquo Advances inAtmospheric Sciences vol 21 no 1 pp 103ndash112 2004

[20] Y C Miao S H Liu H Zheng et al ldquoA multi-scale urbanatmospheric dispersion model for emergency managementrdquoAdvances in Atmospheric Sciences vol 31 no 6 pp 1353ndash13652014

[21] S Miao W Jiang X Wang and W Guo ldquoImpact assessmentof urban meteorology and the atmospheric environment usingurban sub-domain planningrdquoBoundary-LayerMeteorology vol118 no 1 pp 133ndash150 2006

[22] OpenCFD OpenFOAM The Open Source Computational FluidDynamics (CFD) Toolbox 2008 httpwwwopencfdcoukopenfoam

[23] J H Ferziger and M Peric Computational Methods for FluidDynamics Springer Berlin Germany 3rd edition 2001

[24] Z I Janjic ldquoThe step-mountain coordinate physical packagerdquoMonthly Weather Review vol 118 no 7 pp 1429ndash1443 1990

[25] Z I Janjic ldquoThe step-mountain eta coordinate model furtherdevelopments of the convection viscous sublayer and turbu-lence closure schemesrdquoMonthlyWeather Review vol 122 no 5pp 927ndash945 1994

[26] E J Mlawer S J Taubman P D Brown M J Iacono and S AClough ldquoRadiative transfer for inhomogeneous atmospheresRRTM a validated correlated-k model for the longwaverdquoJournal of Geophysical Research Atmospheres vol 102 no 14pp 16663ndash16682 1997

[27] J Dudhia ldquoNumerical study of convection observed dur-ing the winter monsoon experiment using a mesoscale two-dimensionalmodelrdquo Journal of theAtmospheric Sciences vol 46no 20 pp 3077ndash3107 1989

[28] S-Y Hong J Dudhia and S-H Chen ldquoA revised approach toice microphysical processes for the bulk parameterization ofclouds and precipitationrdquoMonthlyWeather Review vol 132 no1 pp 103ndash120 2004

[29] J S Kain ldquoThe Kain Fritsch convective parameterization anupdaterdquo Journal of Applied Meteorology vol 43 no 1 pp 170ndash181 2004

[30] F Chen and J Dudhia ldquoCoupling and advanced land surface-hydrology model with the Penn State-NCAR MM5 modelingsystem Part I model implementation and sensitivityrdquoMonthlyWeather Review vol 129 no 4 pp 569ndash585 2001

[31] H Kusaka H Kondo Y Kikegawa and F Kimura ldquoA simplesingle-layer urban canopy model for atmospheric modelscomparison with multi-layer and slab modelsrdquo Boundary-LayerMeteorology vol 101 no 3 pp 329ndash358 2001

[32] H Kusaka and F Kimura ldquoCoupling a single-layer urbancanopy model with a simple atmospheric model impact onurban heat island simulation for an idealized caserdquo Journal of theMeteorological Society of Japan vol 82 no 1 pp 67ndash80 2004

Advances in Meteorology 15

[33] B Grisogono and J Oerlemans ldquoJustifying the WKB approxi-mation in pure katabatic flowsrdquo Tellus A Dynamic Meteorologyand Oceanography vol 54 no 5 pp 453ndash462 2002

[34] A Jericevic L Kraljevic B Grisogono H Fagerli and Z Vece-naj ldquoParameterization of vertical diffusion and the atmosphericboundary layer height determination in the EMEP modelrdquoAtmospheric Chemistry and Physics vol 10 no 2 pp 341ndash3642010

[35] C Bicheng L ShuhuaM Yucong et al ldquoConstruction and vali-dation of a computational fluid dynamics approach for flow anddispersion modeling in urban areardquo Journal of MeteorologicalResearch vol 27 no 6 pp 923ndash941 2013

[36] C Liqiang and Y Hongbin ldquoSynoptic patterns of regional airpollution in Liaoning Provincerdquo Environmental Pollution ampControl vol 28 no 6 pp 435ndash451 2006 (Chinese)

[37] S A Adachi H KusakaM G Duda et al ldquoImprovement of thesingle-layer UCM in the WRF modelrdquo in Proceedings of the 8thInternational Conference on Urban Climates (ICUC8 rsquo12) 2012

[38] G Roux Y Liu L D Monache et al ldquoVerification of highresolution WRF-RTFDDA surface forecasts over mountainsand plainsrdquo Proceedings of the 10th WRF Usersrsquo Workshop pp20ndash23 2009

[39] S Shimada T Ohsawa S Chikaoka et al ldquoAccuracy of the windspeed profile in the lower PBL as simulated by theWRFmodelrdquoSola vol 7 pp 109ndash112 2011

[40] P A Jimenez and J Dudhia ldquoImproving the representation ofresolved and unresolved topographic effects on surface wind inthe wrf modelrdquo Journal of AppliedMeteorology and Climatologyvol 51 no 2 pp 300ndash316 2012

[41] Z I Janjic ldquoNonsingular implementation of theMellor-Yamadalevel 25 scheme in the NCEP Meso modelrdquo NOAANWSNCEP Office Note 437 2001

[42] X-M Hu J W Nielsen-Gammon and F Zhang ldquoEvaluationof three planetary boundary layer schemes in the WRF modelrdquoJournal of Applied Meteorology and Climatology vol 49 no 9pp 1831ndash1844 2010

[43] J W Nielsen-Gammon C L Powell M J Mahoney et alldquoMultisensor estimation of mixing heights over a coastal cityrdquoJournal of Applied Meteorology and Climatology vol 47 no 1pp 27ndash43 2008

[44] L J Hunter G T Johnson and I D Watson ldquoAn investigationof three-dimensional characteristics of flow regimes withinthe urban canyonrdquo Atmospheric Environment Part B UrbanAtmosphere vol 26 no 4 pp 425ndash432 1992

[45] Y Q Zhang S P Arya and W H Snyder ldquoA comparisonof numerical and physical modeling of stable atmosphericflow and dispersion around a cubical buildingrdquo AtmosphericEnvironment vol 30 no 8 pp 1327ndash1345 1996

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

Advances in Meteorology 11

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

(a)

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

123∘10

998400E 123∘30

998400E 123∘50

998400E

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(b)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(c)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(d)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

(e)

123∘10

998400E 123∘30

998400E 123∘50

998400E

42∘N

41∘50

998400N

41∘40

998400N

41∘30

998400N

41∘20

998400N

6

Reference vector

10

12

14

16

18

20

22

24

26

28

30

Tem

pera

ture

2m

(∘C)

(f)

Figure 9 The 10-m wind vector fields and 2-m temperature fields of Shenyang on 13th of August 2012 (a) 0200 LST (b) 0600 LST (c) 1000LST (d) 1400 LST (e) 1800 LST (f) 2200 LST The location of the CFD model domain is indicated by the square and the area of Shenyangcity is indicated by black solid line

12 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

(c)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

01

05

1

25

5

10

20

35

50

(d)

Figure 10 Simulated concentration (ppm) and wind vector fields at 1400 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

(Summer-Run and Winter-Run) were performed to studythe typical features of the atmospheric boundary layer struc-tures of different season Then the coupled WRF-CFD wasused to study how the atmospheric boundary structureambient wind and source position affect the wind fieldand pollutant distribution within the built-up areas It wasfound that the pollutant dispersion pattern and the pollutiondegree dispersion were complicated in the presence of realbuilding clusters and under varying atmospheric bound-ary structures ambient wind and locations of pollutionsources

From this preliminary numerical study it was found thatthe atmospheric boundary structure played a crucial role onthe pollution within the building cluster which determinedthe potential turbulent diffusion ability of the atmosphericsurface layer For example within a nocturnal stable atmo-spheric boundary condition although the ambient wind

speed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

The change of the ambient wind direction can signifi-cantly affect the dispersion pattern of pollutants which was amore sensitive factor than the ambient wind speedThereforewhen a building cluster was designed it was important toconsider the frequency of the ambient wind direction there

Under a given atmospheric state the location of thepollution source would dramatically determine the pollutionpatterns within the built-up areasWhen the pollutant sourcewas set up on the leeward side of the building the pollutantdispersion pattern was dominated by turbulent diffusion pro-cess which was affected by atmospheric boundary structureswhile the convection process dominated when the pollutantsource was set up in a more open area Besides that thedistribution of pollutant concentrationwas driven by the flowpattern

Advances in Meteorology 13

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

A

B

3

Reference vector

A

B

(a)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

B

(b)

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

A

(c)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

(d)

Figure 11 Simulated concentration (ppm) and wind vector fields at 2200 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

A

B

90

60

30

0

Z(m

)

Y (m)6005004003002001000

Reference vector3

Figure 12 The vertical plane of the wind vector field across 119883 =325m

Finally it should be noted that the wind fields anddispersion patterns within the building clusters were com-plicated which cannot be obtained from the ambient wind

TheWRF-CFD numerical evaluation can be used as a reliablemethod to understand the complicated flow and dispersionwithin the built-up areas

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is supported by the China Meteorological Admin-istration Special Public Welfare Research Fund under Grantno GYHY201106033 and the National Natural Science Foun-dation of China under Grant no 41175004

14 Advances in Meteorology

References

[1] H R Olesen R Berkowicz M Ketzel and P Loslashfstroslashm ldquoVal-idation of OML AERMODPRIME and MISKAM using theThompson wind-tunnel dataset for simple stack-building con-figurationsrdquo Boundary-LayerMeteorology vol 131 no 1 pp 73ndash83 2009

[2] R S Thompson ldquoBuilding amplification factors for sourcesnear buildings a wind-tunnel studyrdquo Atmospheric EnvironmentPart A General Topics vol 27 no 15 pp 2313ndash2325 1993

[3] A F Stein and B M Toselli ldquoStreet level air pollution in Cor-doba City ArgentinardquoAtmospheric Environment vol 30 no 20pp 3491ndash3495 1996

[4] RWMacDonald R F Griffiths and S C Cheah ldquoField exper-iments of dispersion through regular arrays of cubic structuresrdquoAtmospheric Environment vol 31 no 6 pp 783ndash795 1997

[5] R W Macdonald R F Griffiths and D J Hall ldquoA comparisonof results from scaled field and wind tunnel modelling ofdispersion in arrays of obstaclesrdquoAtmospheric Environment vol32 no 22 pp 3845ndash3862 1998

[6] M Pavageau andM Schatzmann ldquoWind tunnel measurementsof concentration fluctuations in an urban street canyonrdquo Atmo-spheric Environment vol 33 no 24-25 pp 3961ndash3971 1999

[7] P Kastner-Klein and E J Plate ldquoWind-tunnel study of concen-tration fields in street canyonsrdquo Atmospheric Environment vol33 no 24-25 pp 3973ndash3979 1999

[8] I Mavroidis R F Griffiths and D J Hall ldquoField and windtunnel investigations of plume dispersion around single surfaceobstaclesrdquo Atmospheric Environment vol 37 no 21 pp 2903ndash2918 2003

[9] DDelaunay D Lakehal C Barre andC Sacre ldquoNumerical andwind tunnel simulation of gas dispersion around a rectangularbuildingrdquo Journal ofWind Engineeringamp Industrial Aerodynam-ics vol 67-68 pp 721ndash732 1997

[10] I R Cowan I P Castro and A G Robins ldquoNumericalconsiderations for simulations of flow and dispersion aroundbuildingsrdquo Journal of Wind Engineering and Industrial Aerody-namics vol 67-68 pp 535ndash545 1997

[11] J J Baik and J J Kim ldquoOn the escape of pollutants from urbanstreet canyonsrdquo Atmospheric Environment vol 36 no 3 pp527ndash536 2002

[12] K Nazridoust and G Ahmadi ldquoAirflow and pollutant transportin street canyonsrdquo Journal of Wind Engineering and IndustrialAerodynamics vol 94 no 6 pp 491ndash522 2006

[13] Y Tominaga SMurakami andAMochida ldquoCFDprediction ofgaseous diffusion around a cubic model using a dynamic mixedSGSmodel based on composite grid techniquerdquo Journal ofWindEngineering and Industrial Aerodynamics vol 67-68 pp 827ndash841 1997

[14] K Sada and A Sato ldquoNumerical calculation of flow andstack-gas concentration fluctuation around a cubical buildingrdquoAtmospheric Environment vol 36 no 35 pp 5527ndash5534 2002

[15] X-X Li C-H Liu and D Y C Leung ldquoLarge-eddy simulationof flow and pollutant dispersion in high-aspect-ratio urbanstreet canyons with wall modelrdquo Boundary-Layer Meteorologyvol 129 no 2 pp 249ndash268 2008

[16] M Tewari H Kusaka F Chen et al ldquoImpact of couplinga microscale computational fluid dynamics model with amesoscale model on urban scale contaminant transport anddispersionrdquo Atmospheric Research vol 96 no 4 pp 656ndash6642010

[17] Y S Liu S G Miao C L Zhang G X Cui and Z S ZhangldquoStudy on micro-atmospheric environment by coupling largeeddy simulation with mesoscale modelrdquo Journal of Wind Engi-neering amp Industrial Aerodynamics vol 107-108 pp 106ndash1172012

[18] Y Miao S Liu B Chen B Zhang S Wang and S Li ldquoSimu-lating urban flow and dispersion in Beijing by coupling a CFDmodel with theWRFmodelrdquoAdvances in Atmospheric Sciencesvol 30 no 6 pp 1663ndash1678 2013

[19] X Fang W Jiang S Miao et al ldquoThe multi-scale numericalmodeling system for research on the relationship betweenurban planning and meteorological environmentrdquo Advances inAtmospheric Sciences vol 21 no 1 pp 103ndash112 2004

[20] Y C Miao S H Liu H Zheng et al ldquoA multi-scale urbanatmospheric dispersion model for emergency managementrdquoAdvances in Atmospheric Sciences vol 31 no 6 pp 1353ndash13652014

[21] S Miao W Jiang X Wang and W Guo ldquoImpact assessmentof urban meteorology and the atmospheric environment usingurban sub-domain planningrdquoBoundary-LayerMeteorology vol118 no 1 pp 133ndash150 2006

[22] OpenCFD OpenFOAM The Open Source Computational FluidDynamics (CFD) Toolbox 2008 httpwwwopencfdcoukopenfoam

[23] J H Ferziger and M Peric Computational Methods for FluidDynamics Springer Berlin Germany 3rd edition 2001

[24] Z I Janjic ldquoThe step-mountain coordinate physical packagerdquoMonthly Weather Review vol 118 no 7 pp 1429ndash1443 1990

[25] Z I Janjic ldquoThe step-mountain eta coordinate model furtherdevelopments of the convection viscous sublayer and turbu-lence closure schemesrdquoMonthlyWeather Review vol 122 no 5pp 927ndash945 1994

[26] E J Mlawer S J Taubman P D Brown M J Iacono and S AClough ldquoRadiative transfer for inhomogeneous atmospheresRRTM a validated correlated-k model for the longwaverdquoJournal of Geophysical Research Atmospheres vol 102 no 14pp 16663ndash16682 1997

[27] J Dudhia ldquoNumerical study of convection observed dur-ing the winter monsoon experiment using a mesoscale two-dimensionalmodelrdquo Journal of theAtmospheric Sciences vol 46no 20 pp 3077ndash3107 1989

[28] S-Y Hong J Dudhia and S-H Chen ldquoA revised approach toice microphysical processes for the bulk parameterization ofclouds and precipitationrdquoMonthlyWeather Review vol 132 no1 pp 103ndash120 2004

[29] J S Kain ldquoThe Kain Fritsch convective parameterization anupdaterdquo Journal of Applied Meteorology vol 43 no 1 pp 170ndash181 2004

[30] F Chen and J Dudhia ldquoCoupling and advanced land surface-hydrology model with the Penn State-NCAR MM5 modelingsystem Part I model implementation and sensitivityrdquoMonthlyWeather Review vol 129 no 4 pp 569ndash585 2001

[31] H Kusaka H Kondo Y Kikegawa and F Kimura ldquoA simplesingle-layer urban canopy model for atmospheric modelscomparison with multi-layer and slab modelsrdquo Boundary-LayerMeteorology vol 101 no 3 pp 329ndash358 2001

[32] H Kusaka and F Kimura ldquoCoupling a single-layer urbancanopy model with a simple atmospheric model impact onurban heat island simulation for an idealized caserdquo Journal of theMeteorological Society of Japan vol 82 no 1 pp 67ndash80 2004

Advances in Meteorology 15

[33] B Grisogono and J Oerlemans ldquoJustifying the WKB approxi-mation in pure katabatic flowsrdquo Tellus A Dynamic Meteorologyand Oceanography vol 54 no 5 pp 453ndash462 2002

[34] A Jericevic L Kraljevic B Grisogono H Fagerli and Z Vece-naj ldquoParameterization of vertical diffusion and the atmosphericboundary layer height determination in the EMEP modelrdquoAtmospheric Chemistry and Physics vol 10 no 2 pp 341ndash3642010

[35] C Bicheng L ShuhuaM Yucong et al ldquoConstruction and vali-dation of a computational fluid dynamics approach for flow anddispersion modeling in urban areardquo Journal of MeteorologicalResearch vol 27 no 6 pp 923ndash941 2013

[36] C Liqiang and Y Hongbin ldquoSynoptic patterns of regional airpollution in Liaoning Provincerdquo Environmental Pollution ampControl vol 28 no 6 pp 435ndash451 2006 (Chinese)

[37] S A Adachi H KusakaM G Duda et al ldquoImprovement of thesingle-layer UCM in the WRF modelrdquo in Proceedings of the 8thInternational Conference on Urban Climates (ICUC8 rsquo12) 2012

[38] G Roux Y Liu L D Monache et al ldquoVerification of highresolution WRF-RTFDDA surface forecasts over mountainsand plainsrdquo Proceedings of the 10th WRF Usersrsquo Workshop pp20ndash23 2009

[39] S Shimada T Ohsawa S Chikaoka et al ldquoAccuracy of the windspeed profile in the lower PBL as simulated by theWRFmodelrdquoSola vol 7 pp 109ndash112 2011

[40] P A Jimenez and J Dudhia ldquoImproving the representation ofresolved and unresolved topographic effects on surface wind inthe wrf modelrdquo Journal of AppliedMeteorology and Climatologyvol 51 no 2 pp 300ndash316 2012

[41] Z I Janjic ldquoNonsingular implementation of theMellor-Yamadalevel 25 scheme in the NCEP Meso modelrdquo NOAANWSNCEP Office Note 437 2001

[42] X-M Hu J W Nielsen-Gammon and F Zhang ldquoEvaluationof three planetary boundary layer schemes in the WRF modelrdquoJournal of Applied Meteorology and Climatology vol 49 no 9pp 1831ndash1844 2010

[43] J W Nielsen-Gammon C L Powell M J Mahoney et alldquoMultisensor estimation of mixing heights over a coastal cityrdquoJournal of Applied Meteorology and Climatology vol 47 no 1pp 27ndash43 2008

[44] L J Hunter G T Johnson and I D Watson ldquoAn investigationof three-dimensional characteristics of flow regimes withinthe urban canyonrdquo Atmospheric Environment Part B UrbanAtmosphere vol 26 no 4 pp 425ndash432 1992

[45] Y Q Zhang S P Arya and W H Snyder ldquoA comparisonof numerical and physical modeling of stable atmosphericflow and dispersion around a cubical buildingrdquo AtmosphericEnvironment vol 30 no 8 pp 1327ndash1345 1996

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

12 Advances in Meteorology

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

(a)

A

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

(b)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

(c)

A

3

Reference vector

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

01

05

1

25

5

10

20

35

50

(d)

Figure 10 Simulated concentration (ppm) and wind vector fields at 1400 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

(Summer-Run and Winter-Run) were performed to studythe typical features of the atmospheric boundary layer struc-tures of different season Then the coupled WRF-CFD wasused to study how the atmospheric boundary structureambient wind and source position affect the wind fieldand pollutant distribution within the built-up areas It wasfound that the pollutant dispersion pattern and the pollutiondegree dispersion were complicated in the presence of realbuilding clusters and under varying atmospheric bound-ary structures ambient wind and locations of pollutionsources

From this preliminary numerical study it was found thatthe atmospheric boundary structure played a crucial role onthe pollution within the building cluster which determinedthe potential turbulent diffusion ability of the atmosphericsurface layer For example within a nocturnal stable atmo-spheric boundary condition although the ambient wind

speed was increased the pollution within the buildings maybe more serious because of the weaker turbulent diffusion

The change of the ambient wind direction can signifi-cantly affect the dispersion pattern of pollutants which was amore sensitive factor than the ambient wind speedThereforewhen a building cluster was designed it was important toconsider the frequency of the ambient wind direction there

Under a given atmospheric state the location of thepollution source would dramatically determine the pollutionpatterns within the built-up areasWhen the pollutant sourcewas set up on the leeward side of the building the pollutantdispersion pattern was dominated by turbulent diffusion pro-cess which was affected by atmospheric boundary structureswhile the convection process dominated when the pollutantsource was set up in a more open area Besides that thedistribution of pollutant concentrationwas driven by the flowpattern

Advances in Meteorology 13

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

A

B

3

Reference vector

A

B

(a)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

B

(b)

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

A

(c)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

(d)

Figure 11 Simulated concentration (ppm) and wind vector fields at 2200 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

A

B

90

60

30

0

Z(m

)

Y (m)6005004003002001000

Reference vector3

Figure 12 The vertical plane of the wind vector field across 119883 =325m

Finally it should be noted that the wind fields anddispersion patterns within the building clusters were com-plicated which cannot be obtained from the ambient wind

TheWRF-CFD numerical evaluation can be used as a reliablemethod to understand the complicated flow and dispersionwithin the built-up areas

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is supported by the China Meteorological Admin-istration Special Public Welfare Research Fund under Grantno GYHY201106033 and the National Natural Science Foun-dation of China under Grant no 41175004

14 Advances in Meteorology

References

[1] H R Olesen R Berkowicz M Ketzel and P Loslashfstroslashm ldquoVal-idation of OML AERMODPRIME and MISKAM using theThompson wind-tunnel dataset for simple stack-building con-figurationsrdquo Boundary-LayerMeteorology vol 131 no 1 pp 73ndash83 2009

[2] R S Thompson ldquoBuilding amplification factors for sourcesnear buildings a wind-tunnel studyrdquo Atmospheric EnvironmentPart A General Topics vol 27 no 15 pp 2313ndash2325 1993

[3] A F Stein and B M Toselli ldquoStreet level air pollution in Cor-doba City ArgentinardquoAtmospheric Environment vol 30 no 20pp 3491ndash3495 1996

[4] RWMacDonald R F Griffiths and S C Cheah ldquoField exper-iments of dispersion through regular arrays of cubic structuresrdquoAtmospheric Environment vol 31 no 6 pp 783ndash795 1997

[5] R W Macdonald R F Griffiths and D J Hall ldquoA comparisonof results from scaled field and wind tunnel modelling ofdispersion in arrays of obstaclesrdquoAtmospheric Environment vol32 no 22 pp 3845ndash3862 1998

[6] M Pavageau andM Schatzmann ldquoWind tunnel measurementsof concentration fluctuations in an urban street canyonrdquo Atmo-spheric Environment vol 33 no 24-25 pp 3961ndash3971 1999

[7] P Kastner-Klein and E J Plate ldquoWind-tunnel study of concen-tration fields in street canyonsrdquo Atmospheric Environment vol33 no 24-25 pp 3973ndash3979 1999

[8] I Mavroidis R F Griffiths and D J Hall ldquoField and windtunnel investigations of plume dispersion around single surfaceobstaclesrdquo Atmospheric Environment vol 37 no 21 pp 2903ndash2918 2003

[9] DDelaunay D Lakehal C Barre andC Sacre ldquoNumerical andwind tunnel simulation of gas dispersion around a rectangularbuildingrdquo Journal ofWind Engineeringamp Industrial Aerodynam-ics vol 67-68 pp 721ndash732 1997

[10] I R Cowan I P Castro and A G Robins ldquoNumericalconsiderations for simulations of flow and dispersion aroundbuildingsrdquo Journal of Wind Engineering and Industrial Aerody-namics vol 67-68 pp 535ndash545 1997

[11] J J Baik and J J Kim ldquoOn the escape of pollutants from urbanstreet canyonsrdquo Atmospheric Environment vol 36 no 3 pp527ndash536 2002

[12] K Nazridoust and G Ahmadi ldquoAirflow and pollutant transportin street canyonsrdquo Journal of Wind Engineering and IndustrialAerodynamics vol 94 no 6 pp 491ndash522 2006

[13] Y Tominaga SMurakami andAMochida ldquoCFDprediction ofgaseous diffusion around a cubic model using a dynamic mixedSGSmodel based on composite grid techniquerdquo Journal ofWindEngineering and Industrial Aerodynamics vol 67-68 pp 827ndash841 1997

[14] K Sada and A Sato ldquoNumerical calculation of flow andstack-gas concentration fluctuation around a cubical buildingrdquoAtmospheric Environment vol 36 no 35 pp 5527ndash5534 2002

[15] X-X Li C-H Liu and D Y C Leung ldquoLarge-eddy simulationof flow and pollutant dispersion in high-aspect-ratio urbanstreet canyons with wall modelrdquo Boundary-Layer Meteorologyvol 129 no 2 pp 249ndash268 2008

[16] M Tewari H Kusaka F Chen et al ldquoImpact of couplinga microscale computational fluid dynamics model with amesoscale model on urban scale contaminant transport anddispersionrdquo Atmospheric Research vol 96 no 4 pp 656ndash6642010

[17] Y S Liu S G Miao C L Zhang G X Cui and Z S ZhangldquoStudy on micro-atmospheric environment by coupling largeeddy simulation with mesoscale modelrdquo Journal of Wind Engi-neering amp Industrial Aerodynamics vol 107-108 pp 106ndash1172012

[18] Y Miao S Liu B Chen B Zhang S Wang and S Li ldquoSimu-lating urban flow and dispersion in Beijing by coupling a CFDmodel with theWRFmodelrdquoAdvances in Atmospheric Sciencesvol 30 no 6 pp 1663ndash1678 2013

[19] X Fang W Jiang S Miao et al ldquoThe multi-scale numericalmodeling system for research on the relationship betweenurban planning and meteorological environmentrdquo Advances inAtmospheric Sciences vol 21 no 1 pp 103ndash112 2004

[20] Y C Miao S H Liu H Zheng et al ldquoA multi-scale urbanatmospheric dispersion model for emergency managementrdquoAdvances in Atmospheric Sciences vol 31 no 6 pp 1353ndash13652014

[21] S Miao W Jiang X Wang and W Guo ldquoImpact assessmentof urban meteorology and the atmospheric environment usingurban sub-domain planningrdquoBoundary-LayerMeteorology vol118 no 1 pp 133ndash150 2006

[22] OpenCFD OpenFOAM The Open Source Computational FluidDynamics (CFD) Toolbox 2008 httpwwwopencfdcoukopenfoam

[23] J H Ferziger and M Peric Computational Methods for FluidDynamics Springer Berlin Germany 3rd edition 2001

[24] Z I Janjic ldquoThe step-mountain coordinate physical packagerdquoMonthly Weather Review vol 118 no 7 pp 1429ndash1443 1990

[25] Z I Janjic ldquoThe step-mountain eta coordinate model furtherdevelopments of the convection viscous sublayer and turbu-lence closure schemesrdquoMonthlyWeather Review vol 122 no 5pp 927ndash945 1994

[26] E J Mlawer S J Taubman P D Brown M J Iacono and S AClough ldquoRadiative transfer for inhomogeneous atmospheresRRTM a validated correlated-k model for the longwaverdquoJournal of Geophysical Research Atmospheres vol 102 no 14pp 16663ndash16682 1997

[27] J Dudhia ldquoNumerical study of convection observed dur-ing the winter monsoon experiment using a mesoscale two-dimensionalmodelrdquo Journal of theAtmospheric Sciences vol 46no 20 pp 3077ndash3107 1989

[28] S-Y Hong J Dudhia and S-H Chen ldquoA revised approach toice microphysical processes for the bulk parameterization ofclouds and precipitationrdquoMonthlyWeather Review vol 132 no1 pp 103ndash120 2004

[29] J S Kain ldquoThe Kain Fritsch convective parameterization anupdaterdquo Journal of Applied Meteorology vol 43 no 1 pp 170ndash181 2004

[30] F Chen and J Dudhia ldquoCoupling and advanced land surface-hydrology model with the Penn State-NCAR MM5 modelingsystem Part I model implementation and sensitivityrdquoMonthlyWeather Review vol 129 no 4 pp 569ndash585 2001

[31] H Kusaka H Kondo Y Kikegawa and F Kimura ldquoA simplesingle-layer urban canopy model for atmospheric modelscomparison with multi-layer and slab modelsrdquo Boundary-LayerMeteorology vol 101 no 3 pp 329ndash358 2001

[32] H Kusaka and F Kimura ldquoCoupling a single-layer urbancanopy model with a simple atmospheric model impact onurban heat island simulation for an idealized caserdquo Journal of theMeteorological Society of Japan vol 82 no 1 pp 67ndash80 2004

Advances in Meteorology 15

[33] B Grisogono and J Oerlemans ldquoJustifying the WKB approxi-mation in pure katabatic flowsrdquo Tellus A Dynamic Meteorologyand Oceanography vol 54 no 5 pp 453ndash462 2002

[34] A Jericevic L Kraljevic B Grisogono H Fagerli and Z Vece-naj ldquoParameterization of vertical diffusion and the atmosphericboundary layer height determination in the EMEP modelrdquoAtmospheric Chemistry and Physics vol 10 no 2 pp 341ndash3642010

[35] C Bicheng L ShuhuaM Yucong et al ldquoConstruction and vali-dation of a computational fluid dynamics approach for flow anddispersion modeling in urban areardquo Journal of MeteorologicalResearch vol 27 no 6 pp 923ndash941 2013

[36] C Liqiang and Y Hongbin ldquoSynoptic patterns of regional airpollution in Liaoning Provincerdquo Environmental Pollution ampControl vol 28 no 6 pp 435ndash451 2006 (Chinese)

[37] S A Adachi H KusakaM G Duda et al ldquoImprovement of thesingle-layer UCM in the WRF modelrdquo in Proceedings of the 8thInternational Conference on Urban Climates (ICUC8 rsquo12) 2012

[38] G Roux Y Liu L D Monache et al ldquoVerification of highresolution WRF-RTFDDA surface forecasts over mountainsand plainsrdquo Proceedings of the 10th WRF Usersrsquo Workshop pp20ndash23 2009

[39] S Shimada T Ohsawa S Chikaoka et al ldquoAccuracy of the windspeed profile in the lower PBL as simulated by theWRFmodelrdquoSola vol 7 pp 109ndash112 2011

[40] P A Jimenez and J Dudhia ldquoImproving the representation ofresolved and unresolved topographic effects on surface wind inthe wrf modelrdquo Journal of AppliedMeteorology and Climatologyvol 51 no 2 pp 300ndash316 2012

[41] Z I Janjic ldquoNonsingular implementation of theMellor-Yamadalevel 25 scheme in the NCEP Meso modelrdquo NOAANWSNCEP Office Note 437 2001

[42] X-M Hu J W Nielsen-Gammon and F Zhang ldquoEvaluationof three planetary boundary layer schemes in the WRF modelrdquoJournal of Applied Meteorology and Climatology vol 49 no 9pp 1831ndash1844 2010

[43] J W Nielsen-Gammon C L Powell M J Mahoney et alldquoMultisensor estimation of mixing heights over a coastal cityrdquoJournal of Applied Meteorology and Climatology vol 47 no 1pp 27ndash43 2008

[44] L J Hunter G T Johnson and I D Watson ldquoAn investigationof three-dimensional characteristics of flow regimes withinthe urban canyonrdquo Atmospheric Environment Part B UrbanAtmosphere vol 26 no 4 pp 425ndash432 1992

[45] Y Q Zhang S P Arya and W H Snyder ldquoA comparisonof numerical and physical modeling of stable atmosphericflow and dispersion around a cubical buildingrdquo AtmosphericEnvironment vol 30 no 8 pp 1327ndash1345 1996

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

Advances in Meteorology 13

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

A

B

3

Reference vector

A

B

(a)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

B

(b)

0 100 200 300 400 500 600

X (m)

600

500

400

300

200

100

0

Y(m

)

3

Reference vector

A

(c)

600

500

400

300

200

100

0

Y(m

)

0 100 200 300 400 500 600

X (m)

3

Reference vector

01

05

1

25

5

10

20

35

50

A

(d)

Figure 11 Simulated concentration (ppm) and wind vector fields at 2200 LST on 13th of August (a b) at 119911 = 25m (c d) at 119911 = 225m (a c)the point source was located at P1 (b d) the point source was located at P2

A

B

90

60

30

0

Z(m

)

Y (m)6005004003002001000

Reference vector3

Figure 12 The vertical plane of the wind vector field across 119883 =325m

Finally it should be noted that the wind fields anddispersion patterns within the building clusters were com-plicated which cannot be obtained from the ambient wind

TheWRF-CFD numerical evaluation can be used as a reliablemethod to understand the complicated flow and dispersionwithin the built-up areas

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work is supported by the China Meteorological Admin-istration Special Public Welfare Research Fund under Grantno GYHY201106033 and the National Natural Science Foun-dation of China under Grant no 41175004

14 Advances in Meteorology

References

[1] H R Olesen R Berkowicz M Ketzel and P Loslashfstroslashm ldquoVal-idation of OML AERMODPRIME and MISKAM using theThompson wind-tunnel dataset for simple stack-building con-figurationsrdquo Boundary-LayerMeteorology vol 131 no 1 pp 73ndash83 2009

[2] R S Thompson ldquoBuilding amplification factors for sourcesnear buildings a wind-tunnel studyrdquo Atmospheric EnvironmentPart A General Topics vol 27 no 15 pp 2313ndash2325 1993

[3] A F Stein and B M Toselli ldquoStreet level air pollution in Cor-doba City ArgentinardquoAtmospheric Environment vol 30 no 20pp 3491ndash3495 1996

[4] RWMacDonald R F Griffiths and S C Cheah ldquoField exper-iments of dispersion through regular arrays of cubic structuresrdquoAtmospheric Environment vol 31 no 6 pp 783ndash795 1997

[5] R W Macdonald R F Griffiths and D J Hall ldquoA comparisonof results from scaled field and wind tunnel modelling ofdispersion in arrays of obstaclesrdquoAtmospheric Environment vol32 no 22 pp 3845ndash3862 1998

[6] M Pavageau andM Schatzmann ldquoWind tunnel measurementsof concentration fluctuations in an urban street canyonrdquo Atmo-spheric Environment vol 33 no 24-25 pp 3961ndash3971 1999

[7] P Kastner-Klein and E J Plate ldquoWind-tunnel study of concen-tration fields in street canyonsrdquo Atmospheric Environment vol33 no 24-25 pp 3973ndash3979 1999

[8] I Mavroidis R F Griffiths and D J Hall ldquoField and windtunnel investigations of plume dispersion around single surfaceobstaclesrdquo Atmospheric Environment vol 37 no 21 pp 2903ndash2918 2003

[9] DDelaunay D Lakehal C Barre andC Sacre ldquoNumerical andwind tunnel simulation of gas dispersion around a rectangularbuildingrdquo Journal ofWind Engineeringamp Industrial Aerodynam-ics vol 67-68 pp 721ndash732 1997

[10] I R Cowan I P Castro and A G Robins ldquoNumericalconsiderations for simulations of flow and dispersion aroundbuildingsrdquo Journal of Wind Engineering and Industrial Aerody-namics vol 67-68 pp 535ndash545 1997

[11] J J Baik and J J Kim ldquoOn the escape of pollutants from urbanstreet canyonsrdquo Atmospheric Environment vol 36 no 3 pp527ndash536 2002

[12] K Nazridoust and G Ahmadi ldquoAirflow and pollutant transportin street canyonsrdquo Journal of Wind Engineering and IndustrialAerodynamics vol 94 no 6 pp 491ndash522 2006

[13] Y Tominaga SMurakami andAMochida ldquoCFDprediction ofgaseous diffusion around a cubic model using a dynamic mixedSGSmodel based on composite grid techniquerdquo Journal ofWindEngineering and Industrial Aerodynamics vol 67-68 pp 827ndash841 1997

[14] K Sada and A Sato ldquoNumerical calculation of flow andstack-gas concentration fluctuation around a cubical buildingrdquoAtmospheric Environment vol 36 no 35 pp 5527ndash5534 2002

[15] X-X Li C-H Liu and D Y C Leung ldquoLarge-eddy simulationof flow and pollutant dispersion in high-aspect-ratio urbanstreet canyons with wall modelrdquo Boundary-Layer Meteorologyvol 129 no 2 pp 249ndash268 2008

[16] M Tewari H Kusaka F Chen et al ldquoImpact of couplinga microscale computational fluid dynamics model with amesoscale model on urban scale contaminant transport anddispersionrdquo Atmospheric Research vol 96 no 4 pp 656ndash6642010

[17] Y S Liu S G Miao C L Zhang G X Cui and Z S ZhangldquoStudy on micro-atmospheric environment by coupling largeeddy simulation with mesoscale modelrdquo Journal of Wind Engi-neering amp Industrial Aerodynamics vol 107-108 pp 106ndash1172012

[18] Y Miao S Liu B Chen B Zhang S Wang and S Li ldquoSimu-lating urban flow and dispersion in Beijing by coupling a CFDmodel with theWRFmodelrdquoAdvances in Atmospheric Sciencesvol 30 no 6 pp 1663ndash1678 2013

[19] X Fang W Jiang S Miao et al ldquoThe multi-scale numericalmodeling system for research on the relationship betweenurban planning and meteorological environmentrdquo Advances inAtmospheric Sciences vol 21 no 1 pp 103ndash112 2004

[20] Y C Miao S H Liu H Zheng et al ldquoA multi-scale urbanatmospheric dispersion model for emergency managementrdquoAdvances in Atmospheric Sciences vol 31 no 6 pp 1353ndash13652014

[21] S Miao W Jiang X Wang and W Guo ldquoImpact assessmentof urban meteorology and the atmospheric environment usingurban sub-domain planningrdquoBoundary-LayerMeteorology vol118 no 1 pp 133ndash150 2006

[22] OpenCFD OpenFOAM The Open Source Computational FluidDynamics (CFD) Toolbox 2008 httpwwwopencfdcoukopenfoam

[23] J H Ferziger and M Peric Computational Methods for FluidDynamics Springer Berlin Germany 3rd edition 2001

[24] Z I Janjic ldquoThe step-mountain coordinate physical packagerdquoMonthly Weather Review vol 118 no 7 pp 1429ndash1443 1990

[25] Z I Janjic ldquoThe step-mountain eta coordinate model furtherdevelopments of the convection viscous sublayer and turbu-lence closure schemesrdquoMonthlyWeather Review vol 122 no 5pp 927ndash945 1994

[26] E J Mlawer S J Taubman P D Brown M J Iacono and S AClough ldquoRadiative transfer for inhomogeneous atmospheresRRTM a validated correlated-k model for the longwaverdquoJournal of Geophysical Research Atmospheres vol 102 no 14pp 16663ndash16682 1997

[27] J Dudhia ldquoNumerical study of convection observed dur-ing the winter monsoon experiment using a mesoscale two-dimensionalmodelrdquo Journal of theAtmospheric Sciences vol 46no 20 pp 3077ndash3107 1989

[28] S-Y Hong J Dudhia and S-H Chen ldquoA revised approach toice microphysical processes for the bulk parameterization ofclouds and precipitationrdquoMonthlyWeather Review vol 132 no1 pp 103ndash120 2004

[29] J S Kain ldquoThe Kain Fritsch convective parameterization anupdaterdquo Journal of Applied Meteorology vol 43 no 1 pp 170ndash181 2004

[30] F Chen and J Dudhia ldquoCoupling and advanced land surface-hydrology model with the Penn State-NCAR MM5 modelingsystem Part I model implementation and sensitivityrdquoMonthlyWeather Review vol 129 no 4 pp 569ndash585 2001

[31] H Kusaka H Kondo Y Kikegawa and F Kimura ldquoA simplesingle-layer urban canopy model for atmospheric modelscomparison with multi-layer and slab modelsrdquo Boundary-LayerMeteorology vol 101 no 3 pp 329ndash358 2001

[32] H Kusaka and F Kimura ldquoCoupling a single-layer urbancanopy model with a simple atmospheric model impact onurban heat island simulation for an idealized caserdquo Journal of theMeteorological Society of Japan vol 82 no 1 pp 67ndash80 2004

Advances in Meteorology 15

[33] B Grisogono and J Oerlemans ldquoJustifying the WKB approxi-mation in pure katabatic flowsrdquo Tellus A Dynamic Meteorologyand Oceanography vol 54 no 5 pp 453ndash462 2002

[34] A Jericevic L Kraljevic B Grisogono H Fagerli and Z Vece-naj ldquoParameterization of vertical diffusion and the atmosphericboundary layer height determination in the EMEP modelrdquoAtmospheric Chemistry and Physics vol 10 no 2 pp 341ndash3642010

[35] C Bicheng L ShuhuaM Yucong et al ldquoConstruction and vali-dation of a computational fluid dynamics approach for flow anddispersion modeling in urban areardquo Journal of MeteorologicalResearch vol 27 no 6 pp 923ndash941 2013

[36] C Liqiang and Y Hongbin ldquoSynoptic patterns of regional airpollution in Liaoning Provincerdquo Environmental Pollution ampControl vol 28 no 6 pp 435ndash451 2006 (Chinese)

[37] S A Adachi H KusakaM G Duda et al ldquoImprovement of thesingle-layer UCM in the WRF modelrdquo in Proceedings of the 8thInternational Conference on Urban Climates (ICUC8 rsquo12) 2012

[38] G Roux Y Liu L D Monache et al ldquoVerification of highresolution WRF-RTFDDA surface forecasts over mountainsand plainsrdquo Proceedings of the 10th WRF Usersrsquo Workshop pp20ndash23 2009

[39] S Shimada T Ohsawa S Chikaoka et al ldquoAccuracy of the windspeed profile in the lower PBL as simulated by theWRFmodelrdquoSola vol 7 pp 109ndash112 2011

[40] P A Jimenez and J Dudhia ldquoImproving the representation ofresolved and unresolved topographic effects on surface wind inthe wrf modelrdquo Journal of AppliedMeteorology and Climatologyvol 51 no 2 pp 300ndash316 2012

[41] Z I Janjic ldquoNonsingular implementation of theMellor-Yamadalevel 25 scheme in the NCEP Meso modelrdquo NOAANWSNCEP Office Note 437 2001

[42] X-M Hu J W Nielsen-Gammon and F Zhang ldquoEvaluationof three planetary boundary layer schemes in the WRF modelrdquoJournal of Applied Meteorology and Climatology vol 49 no 9pp 1831ndash1844 2010

[43] J W Nielsen-Gammon C L Powell M J Mahoney et alldquoMultisensor estimation of mixing heights over a coastal cityrdquoJournal of Applied Meteorology and Climatology vol 47 no 1pp 27ndash43 2008

[44] L J Hunter G T Johnson and I D Watson ldquoAn investigationof three-dimensional characteristics of flow regimes withinthe urban canyonrdquo Atmospheric Environment Part B UrbanAtmosphere vol 26 no 4 pp 425ndash432 1992

[45] Y Q Zhang S P Arya and W H Snyder ldquoA comparisonof numerical and physical modeling of stable atmosphericflow and dispersion around a cubical buildingrdquo AtmosphericEnvironment vol 30 no 8 pp 1327ndash1345 1996

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

14 Advances in Meteorology

References

[1] H R Olesen R Berkowicz M Ketzel and P Loslashfstroslashm ldquoVal-idation of OML AERMODPRIME and MISKAM using theThompson wind-tunnel dataset for simple stack-building con-figurationsrdquo Boundary-LayerMeteorology vol 131 no 1 pp 73ndash83 2009

[2] R S Thompson ldquoBuilding amplification factors for sourcesnear buildings a wind-tunnel studyrdquo Atmospheric EnvironmentPart A General Topics vol 27 no 15 pp 2313ndash2325 1993

[3] A F Stein and B M Toselli ldquoStreet level air pollution in Cor-doba City ArgentinardquoAtmospheric Environment vol 30 no 20pp 3491ndash3495 1996

[4] RWMacDonald R F Griffiths and S C Cheah ldquoField exper-iments of dispersion through regular arrays of cubic structuresrdquoAtmospheric Environment vol 31 no 6 pp 783ndash795 1997

[5] R W Macdonald R F Griffiths and D J Hall ldquoA comparisonof results from scaled field and wind tunnel modelling ofdispersion in arrays of obstaclesrdquoAtmospheric Environment vol32 no 22 pp 3845ndash3862 1998

[6] M Pavageau andM Schatzmann ldquoWind tunnel measurementsof concentration fluctuations in an urban street canyonrdquo Atmo-spheric Environment vol 33 no 24-25 pp 3961ndash3971 1999

[7] P Kastner-Klein and E J Plate ldquoWind-tunnel study of concen-tration fields in street canyonsrdquo Atmospheric Environment vol33 no 24-25 pp 3973ndash3979 1999

[8] I Mavroidis R F Griffiths and D J Hall ldquoField and windtunnel investigations of plume dispersion around single surfaceobstaclesrdquo Atmospheric Environment vol 37 no 21 pp 2903ndash2918 2003

[9] DDelaunay D Lakehal C Barre andC Sacre ldquoNumerical andwind tunnel simulation of gas dispersion around a rectangularbuildingrdquo Journal ofWind Engineeringamp Industrial Aerodynam-ics vol 67-68 pp 721ndash732 1997

[10] I R Cowan I P Castro and A G Robins ldquoNumericalconsiderations for simulations of flow and dispersion aroundbuildingsrdquo Journal of Wind Engineering and Industrial Aerody-namics vol 67-68 pp 535ndash545 1997

[11] J J Baik and J J Kim ldquoOn the escape of pollutants from urbanstreet canyonsrdquo Atmospheric Environment vol 36 no 3 pp527ndash536 2002

[12] K Nazridoust and G Ahmadi ldquoAirflow and pollutant transportin street canyonsrdquo Journal of Wind Engineering and IndustrialAerodynamics vol 94 no 6 pp 491ndash522 2006

[13] Y Tominaga SMurakami andAMochida ldquoCFDprediction ofgaseous diffusion around a cubic model using a dynamic mixedSGSmodel based on composite grid techniquerdquo Journal ofWindEngineering and Industrial Aerodynamics vol 67-68 pp 827ndash841 1997

[14] K Sada and A Sato ldquoNumerical calculation of flow andstack-gas concentration fluctuation around a cubical buildingrdquoAtmospheric Environment vol 36 no 35 pp 5527ndash5534 2002

[15] X-X Li C-H Liu and D Y C Leung ldquoLarge-eddy simulationof flow and pollutant dispersion in high-aspect-ratio urbanstreet canyons with wall modelrdquo Boundary-Layer Meteorologyvol 129 no 2 pp 249ndash268 2008

[16] M Tewari H Kusaka F Chen et al ldquoImpact of couplinga microscale computational fluid dynamics model with amesoscale model on urban scale contaminant transport anddispersionrdquo Atmospheric Research vol 96 no 4 pp 656ndash6642010

[17] Y S Liu S G Miao C L Zhang G X Cui and Z S ZhangldquoStudy on micro-atmospheric environment by coupling largeeddy simulation with mesoscale modelrdquo Journal of Wind Engi-neering amp Industrial Aerodynamics vol 107-108 pp 106ndash1172012

[18] Y Miao S Liu B Chen B Zhang S Wang and S Li ldquoSimu-lating urban flow and dispersion in Beijing by coupling a CFDmodel with theWRFmodelrdquoAdvances in Atmospheric Sciencesvol 30 no 6 pp 1663ndash1678 2013

[19] X Fang W Jiang S Miao et al ldquoThe multi-scale numericalmodeling system for research on the relationship betweenurban planning and meteorological environmentrdquo Advances inAtmospheric Sciences vol 21 no 1 pp 103ndash112 2004

[20] Y C Miao S H Liu H Zheng et al ldquoA multi-scale urbanatmospheric dispersion model for emergency managementrdquoAdvances in Atmospheric Sciences vol 31 no 6 pp 1353ndash13652014

[21] S Miao W Jiang X Wang and W Guo ldquoImpact assessmentof urban meteorology and the atmospheric environment usingurban sub-domain planningrdquoBoundary-LayerMeteorology vol118 no 1 pp 133ndash150 2006

[22] OpenCFD OpenFOAM The Open Source Computational FluidDynamics (CFD) Toolbox 2008 httpwwwopencfdcoukopenfoam

[23] J H Ferziger and M Peric Computational Methods for FluidDynamics Springer Berlin Germany 3rd edition 2001

[24] Z I Janjic ldquoThe step-mountain coordinate physical packagerdquoMonthly Weather Review vol 118 no 7 pp 1429ndash1443 1990

[25] Z I Janjic ldquoThe step-mountain eta coordinate model furtherdevelopments of the convection viscous sublayer and turbu-lence closure schemesrdquoMonthlyWeather Review vol 122 no 5pp 927ndash945 1994

[26] E J Mlawer S J Taubman P D Brown M J Iacono and S AClough ldquoRadiative transfer for inhomogeneous atmospheresRRTM a validated correlated-k model for the longwaverdquoJournal of Geophysical Research Atmospheres vol 102 no 14pp 16663ndash16682 1997

[27] J Dudhia ldquoNumerical study of convection observed dur-ing the winter monsoon experiment using a mesoscale two-dimensionalmodelrdquo Journal of theAtmospheric Sciences vol 46no 20 pp 3077ndash3107 1989

[28] S-Y Hong J Dudhia and S-H Chen ldquoA revised approach toice microphysical processes for the bulk parameterization ofclouds and precipitationrdquoMonthlyWeather Review vol 132 no1 pp 103ndash120 2004

[29] J S Kain ldquoThe Kain Fritsch convective parameterization anupdaterdquo Journal of Applied Meteorology vol 43 no 1 pp 170ndash181 2004

[30] F Chen and J Dudhia ldquoCoupling and advanced land surface-hydrology model with the Penn State-NCAR MM5 modelingsystem Part I model implementation and sensitivityrdquoMonthlyWeather Review vol 129 no 4 pp 569ndash585 2001

[31] H Kusaka H Kondo Y Kikegawa and F Kimura ldquoA simplesingle-layer urban canopy model for atmospheric modelscomparison with multi-layer and slab modelsrdquo Boundary-LayerMeteorology vol 101 no 3 pp 329ndash358 2001

[32] H Kusaka and F Kimura ldquoCoupling a single-layer urbancanopy model with a simple atmospheric model impact onurban heat island simulation for an idealized caserdquo Journal of theMeteorological Society of Japan vol 82 no 1 pp 67ndash80 2004

Advances in Meteorology 15

[33] B Grisogono and J Oerlemans ldquoJustifying the WKB approxi-mation in pure katabatic flowsrdquo Tellus A Dynamic Meteorologyand Oceanography vol 54 no 5 pp 453ndash462 2002

[34] A Jericevic L Kraljevic B Grisogono H Fagerli and Z Vece-naj ldquoParameterization of vertical diffusion and the atmosphericboundary layer height determination in the EMEP modelrdquoAtmospheric Chemistry and Physics vol 10 no 2 pp 341ndash3642010

[35] C Bicheng L ShuhuaM Yucong et al ldquoConstruction and vali-dation of a computational fluid dynamics approach for flow anddispersion modeling in urban areardquo Journal of MeteorologicalResearch vol 27 no 6 pp 923ndash941 2013

[36] C Liqiang and Y Hongbin ldquoSynoptic patterns of regional airpollution in Liaoning Provincerdquo Environmental Pollution ampControl vol 28 no 6 pp 435ndash451 2006 (Chinese)

[37] S A Adachi H KusakaM G Duda et al ldquoImprovement of thesingle-layer UCM in the WRF modelrdquo in Proceedings of the 8thInternational Conference on Urban Climates (ICUC8 rsquo12) 2012

[38] G Roux Y Liu L D Monache et al ldquoVerification of highresolution WRF-RTFDDA surface forecasts over mountainsand plainsrdquo Proceedings of the 10th WRF Usersrsquo Workshop pp20ndash23 2009

[39] S Shimada T Ohsawa S Chikaoka et al ldquoAccuracy of the windspeed profile in the lower PBL as simulated by theWRFmodelrdquoSola vol 7 pp 109ndash112 2011

[40] P A Jimenez and J Dudhia ldquoImproving the representation ofresolved and unresolved topographic effects on surface wind inthe wrf modelrdquo Journal of AppliedMeteorology and Climatologyvol 51 no 2 pp 300ndash316 2012

[41] Z I Janjic ldquoNonsingular implementation of theMellor-Yamadalevel 25 scheme in the NCEP Meso modelrdquo NOAANWSNCEP Office Note 437 2001

[42] X-M Hu J W Nielsen-Gammon and F Zhang ldquoEvaluationof three planetary boundary layer schemes in the WRF modelrdquoJournal of Applied Meteorology and Climatology vol 49 no 9pp 1831ndash1844 2010

[43] J W Nielsen-Gammon C L Powell M J Mahoney et alldquoMultisensor estimation of mixing heights over a coastal cityrdquoJournal of Applied Meteorology and Climatology vol 47 no 1pp 27ndash43 2008

[44] L J Hunter G T Johnson and I D Watson ldquoAn investigationof three-dimensional characteristics of flow regimes withinthe urban canyonrdquo Atmospheric Environment Part B UrbanAtmosphere vol 26 no 4 pp 425ndash432 1992

[45] Y Q Zhang S P Arya and W H Snyder ldquoA comparisonof numerical and physical modeling of stable atmosphericflow and dispersion around a cubical buildingrdquo AtmosphericEnvironment vol 30 no 8 pp 1327ndash1345 1996

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

Advances in Meteorology 15

[33] B Grisogono and J Oerlemans ldquoJustifying the WKB approxi-mation in pure katabatic flowsrdquo Tellus A Dynamic Meteorologyand Oceanography vol 54 no 5 pp 453ndash462 2002

[34] A Jericevic L Kraljevic B Grisogono H Fagerli and Z Vece-naj ldquoParameterization of vertical diffusion and the atmosphericboundary layer height determination in the EMEP modelrdquoAtmospheric Chemistry and Physics vol 10 no 2 pp 341ndash3642010

[35] C Bicheng L ShuhuaM Yucong et al ldquoConstruction and vali-dation of a computational fluid dynamics approach for flow anddispersion modeling in urban areardquo Journal of MeteorologicalResearch vol 27 no 6 pp 923ndash941 2013

[36] C Liqiang and Y Hongbin ldquoSynoptic patterns of regional airpollution in Liaoning Provincerdquo Environmental Pollution ampControl vol 28 no 6 pp 435ndash451 2006 (Chinese)

[37] S A Adachi H KusakaM G Duda et al ldquoImprovement of thesingle-layer UCM in the WRF modelrdquo in Proceedings of the 8thInternational Conference on Urban Climates (ICUC8 rsquo12) 2012

[38] G Roux Y Liu L D Monache et al ldquoVerification of highresolution WRF-RTFDDA surface forecasts over mountainsand plainsrdquo Proceedings of the 10th WRF Usersrsquo Workshop pp20ndash23 2009

[39] S Shimada T Ohsawa S Chikaoka et al ldquoAccuracy of the windspeed profile in the lower PBL as simulated by theWRFmodelrdquoSola vol 7 pp 109ndash112 2011

[40] P A Jimenez and J Dudhia ldquoImproving the representation ofresolved and unresolved topographic effects on surface wind inthe wrf modelrdquo Journal of AppliedMeteorology and Climatologyvol 51 no 2 pp 300ndash316 2012

[41] Z I Janjic ldquoNonsingular implementation of theMellor-Yamadalevel 25 scheme in the NCEP Meso modelrdquo NOAANWSNCEP Office Note 437 2001

[42] X-M Hu J W Nielsen-Gammon and F Zhang ldquoEvaluationof three planetary boundary layer schemes in the WRF modelrdquoJournal of Applied Meteorology and Climatology vol 49 no 9pp 1831ndash1844 2010

[43] J W Nielsen-Gammon C L Powell M J Mahoney et alldquoMultisensor estimation of mixing heights over a coastal cityrdquoJournal of Applied Meteorology and Climatology vol 47 no 1pp 27ndash43 2008

[44] L J Hunter G T Johnson and I D Watson ldquoAn investigationof three-dimensional characteristics of flow regimes withinthe urban canyonrdquo Atmospheric Environment Part B UrbanAtmosphere vol 26 no 4 pp 425ndash432 1992

[45] Y Q Zhang S P Arya and W H Snyder ldquoA comparisonof numerical and physical modeling of stable atmosphericflow and dispersion around a cubical buildingrdquo AtmosphericEnvironment vol 30 no 8 pp 1327ndash1345 1996

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ClimatologyJournal of

EcologyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

EarthquakesJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom

Applied ampEnvironmentalSoil Science

Volume 2014

Mining

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

International Journal of

Geophysics

OceanographyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of Computational Environmental SciencesHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal ofPetroleum Engineering

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

GeochemistryHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

Atmospheric SciencesInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

OceanographyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Advances in

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MineralogyInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

MeteorologyAdvances in

The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Paleontology JournalHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geological ResearchJournal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Geology Advances in