04/20/23

Prediction of the 10 July 2004 Beijing Flood with a High-Resolution NWP model

Ying-Hwa Kuo1 and Yingchun Wang2

1. National Center for Atmospheric Research, USA

2. Beijing Meteorological Bureau, China

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Model Configuration

Two domain, run in two-nested mode Domain 1: 12 km; domain 2: 4 km Physics used in domain 1:

o KF CU, YSU PBL, 5-layer soil model (not LSM), RRTM lw, Dudhia sw

Physics used in domain 2:o Same as in domain 1, except no KFo Two different micropysics options: Lin et al. (1983)

and WSM-6

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Data Used

NCEP Global Forecast System (GFS) final analysis at 1 degree resolution

Radiosonde, surface and AWS observations obtained from Beijing Meteorological Bureau (BMB)

Ground-based GPS PW from Fang Shan obtained from BMB

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Experiments

Control: or experiment Ao GFS data only, used for both IC and BC

3DVAR 1: or experiment Bo GFS + radiosonde, sfc + AWS

3DVAR 2: or experiment Co GFS + radiosonde, sfc + AWS + GPS PW

All experiments start at 1200 UTC 7/9/04 and run for 36 hours

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6-h accumulated rainfall 06-12 UTC 10 July 2004

GFSOBS

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6-h accumulated rainfall 06-12 UTC 10 July 2004

BMB BMB+PWLin et al Microphysics

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Lin et al.BMB+PWWSM-6

6-h accumulated rainfall 06-12 UTC 10 July 2004

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BMB+PW4-km WRFRadar ref.Wind at 1km

Lin et al. microphysics

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BMB+PW4-km WRFRadar ref.Wind at 1km

WSM-6microphysics

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Differences of WSM-6 from Lin et al. microphysics

Differences in the assumption of particle size and number distributions for ice particles.

Melting is done on small fall-term timesteps to make it more accurate as a function of height.

Saturation processes are difference. o Line et al. use some combined ice/water saturation vapor pressure

based on temperature

o WSM-6: Ice particles respond to ice saturation and water particles respond to water saturation.

Accretion of particles takes into account of the fall speeds of both species, not just the faster falling species.

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The GPS network in FangShan Beijing area of China

115.5 116 116.5 117 117.5oE

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HCHDLLHS

YCSS

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54511

RAIN_GAUGE

116 116.2 116.4oE

39.6

No39.8

54511(Brown Square): The Radiosonde Station

RAIN_GAUGE(Green Diamond): The FangShan AWS

Black triangle: Four Single Frequency GPS Stations of BMB

Black circle: Four Dual Frequency GPS Stations of BMB

. 8 GPS Stations with mean distance less than 10km

. A Vaisala AWS(P,T,RH) built on each GPS station

. YSDD->54511 ~ 30 km

. YCSS->RAIN_GAUGE ~ 5km

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Preliminary Conclusions WRF 4-km model initialized with the NCEP GFS analysis did not produce any

precipitation over Beijing. GFS is quite good on the larger scale, it is the mesoscale details that it fails to capture.

WRF 3D-Var assimilation of local data set makes a big difference in the stability of the local convective environment.

Simulation of convective evolution is sensitive to quality of mesoscale analysis and precipitation microphysics

CAPE CIN

GFS 24 -362

BMB 436 -232

BMB + GPS 756 -183