Numerical Simulations And Predictions Of The Bohai Sea Surface Winds

The Bohai Sea is a nearly closed shallow sea with strong winds all through theyear. The strong Sea Surface Winds (SSWs) over the sea caused by cyclones, coldwaves and clod air will result in serious influence to the boats and ships, the harborengineering buildings, the littoral economy, and so on.The numerical simulation is a kind of important means for the forecast of theSSWs over the Bohai Sea. In this paper, a simulation and prediction system of SSWsfor the Bohai Sea areas is established based on the Weather Research and Forecast(WRF) mesoscale model by using the National Centers for Environmental Prediction(NCEP) to provide the initial background fields and time-dependent boundaryconditions and applying various observation data such as3DVAR assimilating withthe Global Telecommunication System (GTS) to optimize the initial fields. In thedoubly nested system,the area with low resolution(30km, mesh size80×80) cancover the whole weather system affecting coastal waters of China and the weathersystem affecting the Bohai Sea upstream in the next48hours; the area with highresolution (10km, mesh size100×100) conducts the high resolution setting for theweather system of the Bohai Sea areas. During the actual running of the system,although using the3DVAR to assimilate with mass land observation data, we foundthat the simulations and predictions of SSWs are not consistent with the true windfields because the lack of the marine observation data results in the low-quality initialfields. To meet the need of the actual requirement, the Cressman successive correctionmethod is taken to optimize the forecast of SSWs by using the observation data fromcoast and island observation stations in the Bohai Sea. In order to prove the correctioneffect, we conduct the check and analysis in the three observation stations of Tanggu,Suizhong, and Longkou using the prediction results of July to August,2010from theBohai SSWs prediction system, and the results show that the guarantee rates of speedand direction of SSWs after correction raise about9%, and reaches82%and72%respectively. So the SSWs after correction are reasonable and believable. Meanwhile,the research result provides a basis for the building of the Bohai sea wind fieldbusiness support system.