南亚高压的东西振荡对湖北省极端暴雨事件的影响分析  

Influences of Vacillation of South Asia High on the Event of Extreme Rainfall of Hubei Province

作　　者：王登炎[1] 周小兰 刘静 

机构地区：[1]武汉中心气象台,武汉430074 [2]湖北气象科技服务中心,武汉430074

出　　处：《暴雨灾害》2010年第2期148-152,165,共6页Torrential Rain and Disasters

基　　金：湖北省气象局课题"77个站1~7天一般性降水;1~5天暴雨;1~3天灾害性暴雨研究"资助

摘　　要：对1975—2008年发生在湖北省及其周边地区的14场24h雨量≥200mm,或48h雨量≥300mm的极端暴雨事件进行了研究。分析发现:极端暴雨事件与南亚高压的东西向移动密切相关。当南亚高压停留在高原上空时,低层南风将孟加拉湾的水汽源源不断地向高原输送,高原西部槽与孟加拉湾水汽汇合,在高原上形成涡旋云系,其在100—200hPa表现为南亚高压脊线东部的反气旋,在500hPa表现为气旋式涡旋。当南亚高压向东移动时,500hPa气旋式涡旋和与之相伴的孟加拉湾水汽也随之向东移动,当副热带高压和低层环境场有利时,极端暴雨事件便发生了。若南亚高压整体东移,则南亚高压中心的巨大辐散场,在低空强辐合配合下,有利于将水汽集中于某地,当中低层形势场有利时,触发极端暴雨事件。若南亚高压部分东移,则南亚高压脊线附近的中尺度反气旋在东移的过程中,触发中尺度对流系统,形成特大暴雨。如果这时有台风登陆,南亚高压形成的高层辐散可使台风低压维持相当长时间而不填塞,最后形成极端暴雨事件。In this paper, the events of extreme rainfall including 14 cases with rainfall≥200mm per 24 hours and rainfall≥ 300mm per 48 hours are studied. It shows that the extreme rainfall are closely related with the east-westly vacillation of South Asia High. When South Asia High stopped above Qinghai-Xizang Plateau, southwest jet of low level translated the water-vapour from the Bay of Bengal to the Plateau, and the vortex cloud system are formed when westly trough of the plateau joins the water vapor from the Bay of Bengal. The vortex cloud system was a deeply mesoscale system corresponding with low vortex and shear line on 500hPa and showing anticyclone near the axis of ridge of South Asia High on 100-200hPa. When the South Asia High moves toward east, the water vapor from the Bay of Bengal also moved eastly. The extreme rainfall event occurs if it meets suitable enviromental field. If South Asia High moves toward east, the great divergence field of the center of South Asia High coordinated by the severe convergence of lower level concentrates the water vapor on a point and triggers the extreme rainfall. If South Asia High partly moves eastly, the mesoscale anticyclone near the axis of ridge of South Asia High moves eastly and triggers mesoscale convective system forming extreme rainfall. If typhoon landed, the divergence of South Asia High makes typhoon maintaining for a considerable long time, and extreme rainfall happens.

关 键 词：南亚高压 东西震荡 极端暴雨 

分 类 号：P458.121.1[天文地球—大气科学及气象学]