辽东半岛和山东半岛地形对黄、渤海大风影响的数值模拟试验

NUMERICAL SIMULATION OF HIGH WIND EVENTS OVER THE YELLOW SEA AND THE BOHAI SEA CONSIDERING TOPOGRAPHIC EFFECTS OF LIAODONG PENINSULA AND SHANDONG PENINSULA

利用WRF模式和地形有无的2种试验方案,对2010年11月26—27日由东移发展的蒙古气旋引发的黄、渤海偏南大风转偏北大风天气过程中,辽东半岛和山东半岛地形对大风强度和分布的影响进行了数值模拟试验。(1)辽东半岛地形对渤海偏南大风和黄海北部偏北大风、山东半岛地形对渤海海峡和黄海北部的偏南、偏北大风均有增幅作用。其中,渤海东北部偏南大风及山东半岛东北部海域偏北大风增幅最大达4 m/s,而山东半岛东北部海域偏南大风和辽东半岛东部海域偏北大风增幅都为2 m/s。(2)地形作用加大了海岸线附近的垂直运动和温度梯度,有利于黄、渤海中尺度强风区的形成和发展。特别是,在辽东半岛东部和山东半岛东北部造成了强风中的极大阵风。(3)地形的强迫作用局部改变了黄、渤海沿岸强风区的分布。地形强迫产生与环境风场同向的扰动时,风力局部增大;反之,风力局部减弱。

A high wind event occurred over the Yellow Sea and the Bohai Sea on November 26 and 27, 2011. Numerical simulation of this event is conducted by using Weather Research and Forecasting （WRF） model. The model output properly depicts the strength and distribution of the high winds over the above areas. In order to examine the topographic influence, a comparative test of simulations with and without the topography is implemented. The results are shown as follows. （1） Topography enhances the wind speed significantly during high winds. The terrain of Liaodong Peninsula enhances a strong southerly wind over the Bohai Sea while the terrain of Shandong Peninsula enhances a strong northerly wind over the Yellow Sea. The incremental southerly wind speed reaches the maxima of 4 m/s over the northeast of the Bohai Sea. The southerly wind speed increases by 2 m/s over waters northeast of the Shandong Peninsula. The northerly wind speed increases by 2 m/s over waters east of the Liaodong Peninsula and by 4 m/s over waters northeast of the Shandong Peninsula. （2） During the high winds, topography contributes to the formation and development of mesoscale strong winds over the Bohai Sea and the Yellow Sea. The terrain affects the enhancement of vertical motion and the temperature gradient near coastal regions, thus leading to the development of a mesoscale vortex within the frontal zone. The generation and development of high wind regions over in the east part of Liaodong Peninsula and northeast part of Shandong Peninsula cause wind gusts in the high wind regions. （3） During high winds, topographic forcing alters the local distribution of strong wind regions over the coastal regions of the two seas. When topographic forcing generates disturbance consistent with the background wind direction, the wind speed increases locally. Adversely, when topographic forcing generates disturbance opposite to the background wind direction, the wind speed decreases locally. West of Liaodong Peninsula, north of Shandong Peninsula and their coastal regions are places where the strong northerly wind prevails. East of Liaodong Peninsula, northeast of Shandong Peninsula and their coastal regions are the regions dominated by strong northerly winds.