华南一次特大暴雨诊断分析及数值模拟

DIAGNOSTIC ANALYSIS AND NUMERICAL STUDY OF A THUNDERSTORM IN SOUTHERN CHINA

用NCEP/NCAR再分析格点资料对2009年5月23-24日发生在华南的特大暴雨过程进行了诊断分析,并利用中国新一代GRAPES模式进行了数值模拟研究。结果表明:副高稳定维持,西侧偏南气流引导季风云团北抬;水汽来源主要为孟加拉湾西南气流和南海东南气流,水汽辐合主要集中在925hPa-850hPa,具有明显日变化特征;垂直上升运动提前约6小时于强降水的出现,暴雨中心位于最大垂直速度中心附近。模式成功模拟了暴雨过程的雨带分布及环流形势演变,显示中尺度涡旋是造成暴雨的主要影响系统,其不仅造成陆地的低层辐合高层辐散,还为暴雨区提供了正涡度,促使2个中α尺度对流系统的生成和发展东移,直接导致暴雨的发生。

Based on the NCEP / NCAR reanalysis gridded data and GRAPES model Diagnostic analysis and Study on Numerical Simulation of Southern China thunderstorm occurred in 23-24 May 2009 is studied. The result shows that moisture sources of torrential rain process comes from Somali cross-equatorial flow, stiff southwest flow of bay of Bengal and the south sea airflow. In periods of torrential rain, stronger convergent winds at lower levels and stronger divergent winds at high levels is conducive to low-level vortex system development and maintenance. Storm center is located near the center of the maximum vertical velocity. It is successful to simulate the large-scale atmosphere circulation development and distribution of torrential rain. It shows that the mesoscale vortex is the main influencing system causing torrential rain, which is in direct relationship with the genesis and intensive development of a meso-α scale low vortex at 850 hPa on the basis of GRAPES model.