台风对西南低涡影响的数值模拟与诊断个例分析

A NUMERICAL SIMULATION AND DIAGNOSES CASE ANALYSIS OF TYPHOON AFFECT ON SOUTHWEST VORTEX

利用NCEP再分析资料和MM5中尺度数值预报模式对2004年9月3～6日因西南低涡造成四川盆地和重庆地区特大暴雨天气过程开展了数值模拟和诊断分析。结果表明，在此次特大暴雨天气过程中，西南低涡生成后由于受“桑达”台风的阻塞影响，西南低涡移动速度变慢，强度增大，生命期延长。同时“桑达”台风西侧吹入内陆的东北气流在西南低涡的东南侧转变为西南气流的过程中出现气流辐合并使得水汽迅速聚积，从而触发了在西南低涡附近形成特大暴雨天气过程。

By use of the NCEP data and MM5 model we simulate the southwest vortex ,which caused the heavy rainfall in Sichuan and Chongqing during September 3-6,2004. The results show that the moving speed of the southwest vortex became slow, and its intensity was enhanced, and its life time extended because the southwest vortex was obstructed by the Sangda typhoon within the heavy rainfall weather process. The warm and damp airflow outside of the Sangda typhoon with a great deal of water vapour began to converge and water vapour began to accumulate rapidly when the northeast airflow,which was blew into the inland,turned to southwest airflow in the southeast of southwest vortex. And then, it induced the heayy rainfall nearby the southwest vortex.