Numerical Simulations of the Boundary Layer Jet off the Southeastern Coast of China

A strong coastal boundary layer jet (CBLJ) (~8 m s super(-1)) off the southeastern coast of China (around 28 degree N, 122 degree E) is found from the July 2006-11 hourly model data simulated by the Advanced Research Weather Research and Forecasting Model (WRF-ARW) with a 9-km horizontal grid. The s...

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Bibliographic Details
Published in:Monthly weather review 2015-04, Vol.143 (4), p.1212-1231
Main Authors: Du, Yu, Chen, Yi-Leng, Zhang, Qinghong
Format: Article
Language:English
Subjects:
Boundary layers
China
Coastal
Coastal environments
Coasts
Computer simulation
Coriolis force
Datasets
Heating
Land
Mathematical models
Meteorology
Mountains
Terrain
Weather
Wind
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Summary:A strong coastal boundary layer jet (CBLJ) (~8 m s super(-1)) off the southeastern coast of China (around 28 degree N, 122 degree E) is found from the July 2006-11 hourly model data simulated by the Advanced Research Weather Research and Forecasting Model (WRF-ARW) with a 9-km horizontal grid. The southerly CBLJ has a jet core at the 925-hPa level, located along the western periphery of the west Pacific subtropical high (WPSH). The CBLJ is mainly contributed by large-scale enhancement by diurnal forcing and orographic effects by the coastal terrain along the southeastern China coast and the terrain of Taiwan. Although the geostrophic winds offshore are faster in the afternoon due to the larger east-west pressure gradient caused by land surface heating over the China plain, the CBLJ has a nocturnal (~0200 LST) maximum. In the afternoon hours, easterly ageostrophic winds driven by differential land-sea thermal heating develop at low levels. After sunset, with the disappearance of land surface heating, the ageostrophic winds offshore veer southward by the Coriolis force and combine with the southerly geostrophic flow resulting in a nocturnal maximum in the CBLJ. Furthermore, from two model sensitivity experiments (NoTW and LowFJ), it is apparent that the terrain of Taiwan and Fujian exerts a secondary influence (1-2 m s super(-1)) on the strength of the CBLJ. The orographic blocking by the terrain of Taiwan and Fujian is more significant with a larger (~1 m s super(-1)) southerly wind component north of the Taiwan Strait at night than in the afternoon hours.
ISSN:0027-0644
1520-0493
DOI:10.1175/MWR-D-14-00348.1