2009 CMAS Conference, 20 October 2009, Chapel Hill, NC.

Fei Chen, Mukul Tewari, Kevin Manning: National Center For Atmospheric Research (NCAR), Boulder, CO

Hiroyuki Kusaka: University of Tsukuba, Japan

Shiguan Miao: Institute of Urban Meteorology, Beijing, China

Alberto Martilli: Centro de Investigaciones Energeticas, Madrid, Spain

Jason Ching: USEPA, Research Triangle Park, NC,

Susanne Grossman Clarke: Arizona State University, Tempe, AZ

XueMei Wang: Sun Yat-Sen University, Guangzhou, China

Applications of the Integrated WRF/Urban Modelling System to

Regional Air Quality

Aspects to the urban environmental problems

• Climate change and human health• Sea-level rise• Indoor and outdoor air quality• Human thermal stress• Water resources and management• Designing livable cities• Atmospheric transport of accidental or

intentional releases of toxic material• Severe weather, flood

The factors that influence urban

environmental risk

Population Increase/

City Growth

Regional and Global Climate Change

and

Extreme Weather

Population Change

City Growth

Urban Physical Effects

on Local Climate and Weather

Regional and Global Climate Change

and Extreme Weather

The factors that influence urban environmental risk

The physical modeling system – A spectrum of coupled scales

Global ScalesGlobal Scales

Continental ScalesContinental Scales

Regional ScalesRegional Scales

Local ScalesLocal Scales

Long Island

Urban ScalesUrban Scales

Current technology for operational weather and climate prediction

Urban Modeling for Weather Research and Forecast (WRF) Model

• WRF is widely used in both operational and research community.

• We can now bridge the gap between traditional mesoscale (~ 10 km) and fine-scale urban transport and dispersion modeling (~ 10 m)

– WRF, new generation NWP model, running with 1-4 km grid spacing

– Availability of new data at urban scales, urban canopy models

– Land data assimilation techniques – Techniques to couple mesoscale and CFD (LES) models.

• Hence, the WRF model is able to deal with regional climate, fine-scale weather forecast, and urban scales air quality and transport and diffusion (T&D).

Integrated WRF Urban Modeling Framework Meet both numerical weather prediction (NWP) and air quality (including T&D) modeling requirements

The Noah Land Model• Noah LSM primarily for NWP, air

pollution, and regional hydrology applications.

• Noah has been implemented in NCEP, AFWA, and oversea-agency operational models.

• Two urban canopy models (UCM)– Single layer urban-canopy

model (SLUCM, based on Kusaka 2001). Released in WRF V2.2 (Dec. 2006).

– Multi-layer UCM (Building Effect Parameterization, BEP) by Martilli et al. (2002). Released in WRF V3.1 (April 2009).

Natural surface

Urban canopy models: Man-made surface Coupled through ‘urban fraction’

Chen et al., 2009, Intl. J. Climatology

IU+1

IU

IU-1

Vertical levels in the UCP BEM

The Building Energy Model (BEM) is inlcued in the Multi-layer BEP

For each floor, BEM solves prognostic equations for indoor air temperature and air moisture by considering:

• generation of heat due to the occupants and equipments.• radiation entering from the windows• interchange of heat and moisture with the exterior through ventilation• heat diffusion through the walls.

!! We do not attempt to simulate a specific building, rather an average behaviour over the grid cell!! Salamanca and Martilli (2009, Theoreti. Appli. Climatol.)

Indoor-outdoor exchange model

Requires detailed mappings of buildingsNational Urban Database and Access Portal Tool

(NUDAPT), led by Jason Ching (USEPA)

Ching et al., 2009, Bull. American Meteorol. Soc.

Example of NUDAPT gridded urban canon parameters for Houston, Texas. Plan area density (PAD), frontal area density of the buildings (FAD).

Applications of Coupled WRF-Urban Models

Houston: Diurnal cycle of wind profile (TexAQS-2000)

Hong Kong: 10-day surface wind

Beijing, Taipei, and Tokyo: surface weather, precipitation

Salt Lake City: Diurnal wind direction (URBAN-2000)

Liu, Chen, Warner, and Basara: 2006, J Appli. Meteorol.Lo, Lau, Chen, and Fung, 2007: J. Appli. Meteorol.Lo, Lau, Fung, and Chen, 2007: J Geophys. Res.Miao and Chen, 2008: Atm. Res. Lin et al., 2008: Atm. Environ.Jiang et al. 2008: J Geophys. Res.Miao et al., 2009: J. Appli. Meteorol. Climatol.Zhang et al., 2009: J Geophys. Res.Tewari et al., 2009: Atm. Res..

Oklahoma City: 2-m temperature (JU-2003)

WRF/urban 4-km regional climate simulation are able to capture urban heat islandsMonthly mean surface air temperatureat 2 m in the Tokyo area at 0500 JST in August averaged for 2004-2007

Observations WRF-Slab land model WRF-Noah-SLUCM

Kusaka et al., 2009, ICUC-7

Rapid Urban Growth in China

YRD: Yangtze River Delta region PRD: Pearl River Delta region

Such urban growth resulted in ozone increaseWRF 12-km monthly (March 2001) averaged difference (urban - preurban)

of the surface ozone (in ppbv) and relative 10-m wind vectors

Daytime Nighttime

Wang et al., 2009, Adv. Atmosp. Physics

2000

2030

industrial or commercialhigh intensity residential low intensity residential

How does future climate change and urban growth modify air pollution in Houston?

Urban expansion Impacts• meteorology:

Temperature Boundary layer depth

•Emissions Biogenic emissions Anthropogenic emissions

Houston in 2000

Projected Houston growth in 2030

2.6

3.5

6.2

4.9

4.2

9.1

0

1

2

3

4

5

6

7

8

9

10

Climate effect Land-use effect Combined effect

Ozo

ne I

ncre

ase

(ppb

)

Zone A Zone B

Results:Results: Land-use change (urbanization) has similar effect on future 8-hour Ozone concentrations to climate change, based on 4-km WRF-Chem simulations.

Jiang et al., 2008, JGR.

Increase of surface ozone by climate change along Increase of surface

ozone by urban growth

Increase of surface ozone by urban growth and climate change

WRF downscale and upscale coupling strategies

Mesoscale modeling system:WRF-Noah/UCM forecast model

Urban T&D modeling system:EULAG LES/CFD model

WRF provides initial and lateral boundary conditions for EULAG in two modes • Isolated sounding data mode – short term, quasi steady conditions, small scale urban domain• Unsteady (temporal-based coupling) mode – linear interpolation of the WRF data in time and space→ Building geometry flow features resolved explicitly with immersed boundary (IB) approach

Coupler:

MCEL Library

Turbulence and wind fields explicitly resolved by EULAG are feedback to WRF-urban• EULAG fields are volumetrically averaged to (coarser) WRF mesh• WRF urban framework introduce source terms in the momentum and turbulence equations→ The coupling impact urban and downstream weather forecast

Upscale data transfer:

Downscale data transfer

Coupled WRF/urban-LES/CFD model results

Dispersion footprint for IOP6 0900 CDT release for Oklahoma City downtown area, Oklahoma) calculated with WRF/EULAG.

Density of SF6 tracer gas (in parts per thousand) 60 minutes after the third release, CFD-urban simulations are contoured. The dots represent the observed density at sites throughout the downtown area of Salt Lake City, Utah. Tewari et al. (2009).

CFD-urban use single sounding

CFD-urban use WRF 12-hforecast

Summary• An international, collaborative effort has developed an

integrated, cross-scale WRF/urban modeling capability, and evaluated it against surface and PBL observations obtained from major cities.

• WRF/urban (WRF-Chem/uban) is a useful tool for addressing various indoor and outdoor air quality problems in cities.

• Muck work remains to be done: identify model and parameter uncertainties, to incorporate urban canopy parameters (detailed building data, remote-sensing, and extrapolation approach.

• The AMS 9th Symposium on the Urban Environment will be held in August 2010, Co-chaired by Fei Chen and Julie Lundquist.