台风“榴莲”陆上维持及暴雨增幅的大尺度环流特征

Large Scale Circulation Features of the Maintenance and Increase in Torrential Rains from the Landing Typhoon Durian

利用"CMA-STI热带气旋最佳路径集"、NCEP/NCAR再分析资料及地面加密观测资料,分析了2001年0103号台风"榴莲"陆上维持及暴雨增幅的大尺度环流特征。结果表明,"榴莲"登陆后正好位于低压带中,中纬度西风槽加强南伸,构成典型的"北槽南涡",阻碍西太平洋副热带高压西伸,使得"榴莲"陆上长时间维持。西风槽后的西北气流将中纬度冷空气输送至低纬,在"榴莲"环流北部外围与东南风暖湿气流汇合,有利于强降水发生。此外,索马里和100°E越赤道气流增强显著,加强西南季风,从阿拉伯海东部,经孟加拉湾和中南半岛中南部,直至南海北部到广西大部形成一条完整的水汽输送带,充沛的水汽直达"榴莲"东北侧,有利于该时段暴雨增幅。低纬夏季风10～20天低频振荡处于极端活跃位相时,低纬低频西风偏北及低频水汽向北输送至广西南部,有利于低层辐合并提供充足水汽,对"榴莲"暴雨增幅有重要作用。

Using the dataset of CMA-STI Tropical Cyclone Optimal Tracks,NCEP/ NCAR reanalysis,and the intensive surface observations,the large scale circulation features of the maintenance and increase in torrential rains from the landing typhoon Durian （0103） were studied. The results showed that Durian,after landing,was just located in the low pressure zone,forming a pattern of ＂north trough and south vortex＂ with a strongly developing mid-latitude westerly trough,which blocked the strengthening and westward extension of western Pacific subtropical high,allowing Durian＇s cyclonic circulation to be maintained. The northwest flow behind the trough transported the cold air from the mid-latitude to the low-latitude and converged southeast warm moist air in Durian＇s northern periphery,leading to the occurrence of heavy precipitation. In addition,the Somalia and 100°E cross-equatorial flow increased significantly with the result that the southwest monsoon was enhanced and a whole band of high-valued vapor fluxes stretched from the eastern Arabian Sea via the Bay of Bengal,central and southern Indo-China Peninsula and the northern South China Sea into Guangxi,which transported abundant vapor into northeast of Durian,making for the increasing of precipitation during this period. When in an extremely active stage of the 10-20 day intraseasonal oscillation of low latitude summer monsoon,low-frequency west winds and vapor northward spread to the south of Guangxi,thus responsible for convergence at lower levels and providing plentiful vapor,which played an important role in the sharp increase in rainfall from Durian.