福建中南部台风远距离突发性暴雨成因分析

对2003年9月20日福建中南部突发性暴雨分析表明，远距离转向北上台风彩云对暴雨的产生起了重要的组织和促进作用，它通过大气环流的调整，促使了地形性低压的发展和西风带低槽的加深，加强了北方冷空气的南侵和锋区的南压，对暴雨的发生起了关键的触发作用；台风西侧外流下沉气流向西的流出气流加强了中尺度低涡的低层气流流入，并与暴雨区的上升气流构成次级环流，加强了对流云团的发展。

Formation Analysis of Sudden Heavy Rain far from Typhoon

Analysis of sudden heavy rain in the middle and south of Fujian Province on Sept. 20, 2003 is made. Results show that Typhoon Choi-wan, turning to north far away, plays an important role of organizer and promoter in the formation of the heavy rain. Through the adjustment of the general circulation, the typhoon makes an orographic depression and a westerly trough develop. As a result, the cold air invades southwards more intensively, which is a key trigger for the heavy rain. The outflows downward at the west side of the typhoon enhanced the low level inflows of a mesoscale vortex and constituted a secondary circulation together with the updrafts over the heavy rain area, which strengthen the development of the convective cloud clusters.