广东后汛期季风槽暴雨天气形势特征分析

Synoptic Analysis of Heavy Rain Related to Monsoon Trough in the Latter Flood Season of Guangdong

对1981～2002年广东后汛期季风槽暴雨期间的环流形势和天气系统进行了统计分析,结果发现,广东后汛期的季风槽暴雨多数发生在西太平洋副高位置偏东或偏南的情况下,并与中纬西风槽或ITCZ有直接联系;季风槽多数位于华南地区上空或华南沿岸海面;高层辐散覆盖广东全部或大部,中心在华南近海.西南季风向北推进源于西南和华南地区低压槽发展,或由于热带气旋登陆后北上而牵动西南季风深入华南陆地,也有些过程是副高西端的偏南气流引导南海季风北进.对流活动有从南海北部或北部湾附近向华南移动的趋势,并有昼夜变化.

Synoptic characteristics associated with heavy rain brought by monsoon trough in the latter flood season of Guangdong from 1981 to 2002 are analyzed. The result indicates that most of the cases take place when the Pacific subtropical high is inclined to the east or in lower latitude than its normal position and are directly related with the westerly troughs or ITCZs. Most monsoon troughs lie over South China or it coastal water. The divergence areas at 200hPa level usually cover the whole Guangdong or the most part of it with the divergence center over the offshore area of South China. The advancing northward of the monsoon is mainly resulted from the development of the trough over Southwest China and South China and the northward movement of the tropical cyclones. The southerly flows on the western periphery of subtropical ridge sometimes could steer the monsoon northward too. As a result, the convection tends to move from the South China Sea and Beibuwan Gulf and its neighboring area toward Guangdong and with a daily variation.