Assessment of Environmental Impact for AWS Observation Data Using a

Computational Fluid Dynamics Model

Jae-Jin KimJae-Jin Kim11, Do-Yong Kim, Do-Yong Kim11, Bok-Haeng Heo, Bok-Haeng Heo22, and Jae-Kwang Won, and Jae-Kwang Won22

11Pukyong National UniversityPukyong National University22Korean Meteorological AdministrationKorean Meteorological Administration

TECO 2012, Brussels BelgiumTECO 2012, Brussels Belgium

Background

▪ Korean Meteorological Administration (KMA) enacted a law on ‘Weather Observation Standardization (WOS)’ in 2006.

▪ Currently, conducting WOS project for 26 observational organs & 3,469 observational facilities.

▪ For scientific/objective evaluation & management, KMA conducted a planning project on ‘Weather Observational Environment Simulator (WOES)’ in 2010.

▪ This study has been performed from 2011, following up

the WOES project.

▪ Evaluation for 14 AWSs/ASOSs in 2011

Kangnam AWS

400

Kangnam AWS

400

Yangcheon AWS

405

Yangcheon AWS

405

Pyoungteak AWS

551

Pyoungteak AWS

551Seogu AWS 846

Seogu AWS 846

Dongreagu

AWS 940

Dongreagu

AWS 940

N. Kangneong ASOS 104

N. Kangneong ASOS 104

Gochang ASOS 174Gochang ASOS 174

Suncheon

ASOS 174

Suncheon

ASOS 174

Deagu ASOS 143

Deagu ASOS 143

Jeju ASOS 184

Jeju ASOS 184

Kangneong ASOS 105

Kangneong ASOS 105

Gochanggun ASOS 251Gochanggun ASOS 251

JuamASOS 256

JuamASOS 256

▪ 15 ASOSs in 2012 - focusing on wind and direct solar

radiationSeoul ASOSSeoul ASOS

Deajeon ASOSDeajeon ASOS

Busan ASOS

Busan ASOSKwangj

u ASOSKwangju ASOS

Chupungryoung ASOS

Chupungryoung ASOS

Ulsan ASOSUlsan ASOS

Boseong AWS

Boseong AWS

Jeonju ASOS

Jeonju ASOS

Chuncheon ASOSChuncheon ASOS

Icheon ASOS

Icheon ASOS

Namwon ASOSNamwon ASOS

Gumi ASOSGumi ASOS

GosanASOS

GosanASOS

Deakwanryoung ASOS

Deakwanryoung ASOS

Uljin ASOSUljin ASOS

urbanurban

ruralrural

standard

standard

Computational Fluid Dynamics (CFD) model

3D, nonhydrostatic, nonrotating, Boussinesq k- turbulence closure sheme

resolution terrain following, sigma - building (obstacle) shape

Meteorological Model

- extremely complex- highly nonlinear

urban flow/dispersion

▪ Target Areas

1) Kangnam AWS

– located in a highly congested area (urban)

2) Gochang ASOS

– transferred on May 15, 2007

– conducted as a standard observatory

3) Seoul ASOS

– class 1 for surface wind, class 4 for direct radiation

AWS

▪ 16 different inflow directions for AWSs & ASOSs▪ wind data at AWS/ASOS are compared with inflow

NENE

SESE

NW

NW

SWSW

NN

EEWW

SS

NN

EN

NE

ESEESE

WNWNWW

SSW

SSW

ENEENE

SSE

SSE

NN

WN

NW

WSWSWW

inflow AWS

▪ Kangnam AWS

Results and Discussion

Higher than AWS

▪ located in a highly congested area▪ building complexes in the north, east, and west directions▪ park in the south direction

AWS

▪ Inflow vs AWS

[wind speed]

[wind direction]

the same as inflow

the ESE (112.5°) and NW (315°) cases

wind speed ratio area fraction

~ 20( ~ 1.18 m s-1) 11.51

~ 40( ~ 2.37 m s-1) 10.39

~ 60( ~ 3.55 m s-1) 15.44

~ 80( ~ 4.73 m s-1) 19.56

~ 100( ~ 5.92 m s-1) 18.13

~ 120( ~ 7.10 m s-1) 23.30

~ 140( ~ 8.28 m s-1) 1.67

~ 160( ~ 9.46 m s-1) 0.01

~ 180( ~10.65 m s-1) 0.00

~ 200( ~11.83 m s-1) 0.00

▪ wind speed ratio to inflow for east-south-east (112.5°) - larger decrease in wind speed but no change in wind direction

▪ flow acceleration in the upwind region due to ‘channeling effect’▪ flow deceleration in the downwind region due to ‘building drag’

acce

lera

tion

dec

eler

atio

n

inflow

(m)

▪ wind vector for north-west (315°) - largest decrease in wind speed and large change in wind direction

inflow

▪ Reproducing AWS wind data using a WRF-CFD model

[period: Apr. 03 – Apr. 09, 2008]

0 20 40 60 80 100 120 140 1600

45

90

135

180

225

270

315

360

AWS WRF WRF-CFDCol 1 vs Col 5

0 20 40 60 80 100 120 140 160

0

2

4

6

8

10

12

14

16

win

d di

rect

ion

win

d sp

eed

time (hr)

RMSE

▪ WRF = 3.11 m s-1

▪ WRF-CFD = 1.35 m s-1

(43%)

▪ wind direction – very strong dependency on WRF▪ wind speed – more realistic reproducing of AWS data than WRF

AWSWRFWRF-CFD

before transfer- conducted to May 14, 2007- apartment complex (12 stories) in the north and northeast, small buildings in the west- low mountain from south to north in the east

after transfer- conducted from May 15, 2007- no higher building around- ASOS built in flat terrain and higher than around

▪ Gochang ASOS – a standard observatory (2007. 05.)

[wind speed]

[wind direction]

before

after

▪ Inflow vs AWS

② 고 창 군 ASOS(ASOS 251) → 고 창 ASOS(ASOS 172) ▪ wind vector for north (360°) before transfer

- larger decrease in wind speed and no change in wind direction

(m)

ASOS

inflow

(%)

wind speed ratio area fraction

~ 20( ~ 1.18 m s-1) 0.89

~ 40( ~ 2.37 m s-1) 0.17

~ 60( ~ 3.55 m s-1) 0.28

~ 80( ~ 4.73 m s-1) 2.94

~ 100( ~ 5.92 m s-1) 59.3

~ 120( ~ 7.10 m s-1) 36.43

~ 140( ~ 8.28 m s-1) 0.00

~ 160( ~ 9.46 m s-1) 0.00

~ 180( ~10.65 m s-1) 0.00

~ 200( ~11.83 m s-1) 0.00

▪ wind speed ratio for south (180°) after transfer - no change in wind direction but ~25 % decrease in wind speed

▪ ASOS in the deceleration zone induced by far upwind buildings▪ mostly (96%) equivalent to inflow

inflow

▪ wind speed ratio averaged for 16

before

▪ well representing background wind after transfer▪ worthy of a standard observatory (surface wind)

after

▪ Seoul ASOS

▪ ‘class 1 & 4’ for wind & DR from a survey using HemiView & NAOBS data

▪ no higher building than the observation filed except for one building

in the northwest (5 m) and an observatory building (5 m)

▪ open from southeast to northwest

satisfying the obstacle restriction of the ‘class 1’ standard

ASOS

▪ slight change in wind direction but relatively large decrease in wind speed

▪ even in the cases of no building higher in the upwind region (from SE to NW)

Inflow direction

0.0 22.5 45.0 67.5 90.0 112.5 135.0 157.5 180.0 202.5 225.0 247.5 270.0 292.5 315.0 337.5 360.0 22.5 45.0

Win

d d

irec

tio

n

0.0

22.5

45.0

67.5

90.0

112.5

135.0

157.5

180.0

202.5

225.0

247.5

270.0

292.5

315.0

337.5

360.0

22.5

45.0

[wind speed]

[wind direction]Inflow

speed

no building

▪ Inflow vs AWS

▪ wind vector and wind speed ratio for southwest (225°)

▪ ASOS in deceleration zone behind the mountain in the south west

▪ resultantly ~45% decrease despite no higher building in the upwind region

inflo

w

S

WN

E

NW

SE

KASIModel

N W

SE

▪ validated against data from Korea Astronomy & Space Science Institute (KASI)▪ the same solar locations

8:00 AM

5:00 PM

▪ Model for direct radiation & sunshine duration - using solar angle and buildings for special application to urban

areas

▪ Application to Seoul ASOS - no cloud day in winter (Dec. 6, 2008) - shadow is long enough to investigate the obstacle’s interference

07:32

17:13

KASI & Model (no topo nor building)

latitudelongitudeheight

08:00 09:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00ASOS 0 1 1 1 1 1 1 1 1 0.9 0

model(avg)

0.13 1 1 1 1 1 1 1 1 0.95 0

07 08 09 10 11 12 13 14 15 16 17 18

1.0

0.0

time

dire

ct r

adia

tion

ASOS model – 1 min model – 1 hour average

Sunrise – 07:52, Sunset – 16:58

Interference of topography and buildings

▪ ASOS vs Model - topography + buildings - ASOS: hourly averaged (1 – full sunshine, 0 – no sunshine)

Slight difference results from model (building) resolution

c.f.) KASI sunrise – 07:32 sunset – 17:13

▪ Interference by buildings

VS

08:00 09:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00with buildings 0.13 1 1 1 1 1 1 1 1 0.95 0

without buildings 0.13 1 1 1 1 1 1 1 1 1 0.21

▪ Late sunrise is caused by topography but early sunset is caused by buildings

▪ Shade (less than 30%, satisfied for class 4) by far upwind buildings

not by the observatory building or building in the northwest

17:13 no interference by buildings interference by buildings

More detail information is required, including obstacle’s orientation, far upwind area information, site elevation/location, and so on.

resulted from considering only the obstacles near observatories

▪ Survey study vs Model results

· class 1 for surface wind? - yes, for just the SE ~ NW cases

· class 4 for direct radiation - based on buildings just around the observatory

previous survey study

· large decrease in wind speed even for the SE ~ NW cases sufficient for class 1?

· satisfying class 4 but caused by far upwind buildings

model result

discrepancy

Summary and Conclusion▪ Evaluating the observational environment for AWSs & ASOSs focusing on surface wind and direct radiation

▪ Systematic & quantitative analysis KN – larger decrease in wind speed due to buildings – WRF-CFD improved the RMSE GC – well representing background wind as a standard observatory after transfer SU – discrepancy between the previous survey and this studies, implying more systematic and detailed method required for classification

▪ CFD model can be used for evaluation & classification of AWS and/or ASOS

This study was supported by the national meteorological observation-standardization

project of Korean Meteorological Administration