“09.4.15”渤海和山东强风过程的动力学诊断分析

2009年4月15日,渤海和山东大部出现了一次强风天气过程。本次过程具有强度大、持续时间短、强风在渤海及山东附近显著加强等特点。为探讨强风的成因,根据常规观测资料以及NCEP分析资料进行了诊断分析。结果表明,本次强风过程是在低层冷锋、高层低涡横槽影响下产生的。冷空气向南推进过程中,冷平流中心由高层向低层传播,850 hPa以下冷平流不断加强,使冷锋不断增强。冷空气到达渤海湾后,锋前的强暖平流与锋后的强冷平流造成低空锋区进一步增强。冷锋次级环流的下沉运动与地面正变压中心对应,变压梯度风与大尺度气压梯度风共同造成强风过程,而强风中的阵风可能与次级环流的强烈脉动有关。

Dynamic Diagnostic Analysis of the 15 April 2009 Gale Wind over the Bohai Sea and Shandong Province

A gale with wind force scale 8 occurred in the Bohai Sea and Shandong Province on 15 April 2009. The gale is severe strong, but lasts only a half day. Wind speed strengthens significantly near the Bohai Sea and Shandong Province. With the conventional surface data and NCEP analysis data, the causes for this gale event are diagnosed. Results show that the gale is affected by the cold front near the surface and the vortex at the upper level. The cold advection spreads downwards from the upper level during the southward moving of the cold air, as a result, the cold advection and the cold air under the 850 hPa both strengthen. When the cold air arrives at the Bohai Sea, the strong cold advection behind and the strong warm advection in front of the cold air at the low level make the frontal zone further strengthening. The downdraft of the secondary circulation is corresponding to the positive allobaric area near the surface. The strong allobaric wind and the large scale baric gradient wind both lead to the abnormal gale together, and the corresponding severe gust wind is probably related to the impulse of the secondary circulation.