引发四川盆地东部暴雨的西南低涡结构特征研究  

Study on Structure Characteristic of Southwest Vortex Accompanying with Heavy Rainstorm in East Sichuan Basin

作　　者：江玉华[1,2] 杜钦 赵大军[4] 何跃 李江 

机构地区：[1]中国气象科学院灾害天气国家重点实验室 [2]重庆市气象台 [3]重庆市气象科学研究所 [4]93762部队气象台 [5]重庆市气象科技档案馆

出　　处：《高原气象》2012年第6期1562-1573,共12页Plateau Meteorology

基　　金：中国气象科学院"灾害天气国家重点实验室"基金项目(2008LASW-B08);重庆市自然科学基金计划重点项目(CSTC;2008BA0022);重庆市气象局科技计划项目(zl-200901;zl-201002)共同资助

摘　　要：利用1951-2008年四川盆地(27°-32°N,105°-110°E)54个地面气象观测站网监测的日雨量资料,分析了四川盆地东部暴雨发生的气候特征。结果表明,四川盆地东部暴雨(或伴有雷雨大风、冰雹大风等)多发生在6-9月,川东北和渝东北是单站暴雨的高发区,重庆西部是大范围暴雨的多发区;引发四川盆地东部(宜宾、南充和重庆西部)暴雨的主要天气系统是西南低涡。对2007-2010年6次西南低涡暴雨过程进行了合成分析,分析表明,西南低涡热力结构特征具有200hPa存在明显增暖现象,对流层中低层则由暖转冷;西南低涡初期大气对流性不稳定明显;西南低涡动力结构特征具有200hPa西风急流在36°N附近,500hPa低槽东移,槽前正涡度加强,从对流层底垂直伸展到300hPa以上,正涡度中心随高度向西倾斜,850～500hPa平均正涡度大值区与低涡中心对应,对流层中低层北风大值区与南风大值区在低涡中心附近形成强水平风切变,同时低涡中心附近的垂直风切变也较明显。促使西南低涡发展的水汽主要来自南海,低空急流由南向北输送水汽,将对流层低层到大气边界层内的水汽输送到低涡中心附近。西南低涡发生、发展过程中在红外卫星云图上具有MCC等中-α尺度特征,发展强盛的西南低涡在多普勒天气雷达回波上有"列车效应"和中气旋特征。Based on daily precipitation datasets from 1951to 2008at 54stations in east Sichuan basin（27°-32°N,105°-110°E）,the results of the daily precipitation statistics show that the heavy rainstorm with storm,hail and strong wind usually occurs from June to September.The high incidence area of single station rainstorm is in the Northeast of Sichuan and Chongqing.Frequent occurred area of regional heavy rainstorm is in the western of Chongqing and southeast of Sichuan.Using the observational data and NCEP/NCAR 1°×1°reanalysis data,selecting six cases with regional heavy rainstorm processes in Yibin,Nanchong and west of Chongqing from 2007to 2010,using the composited method,an analysis is made for the dynamic and thermal structure and moisture conditions of the influence system which promotes the occurrence and development of Southwest Vortex（SWV）.The results show that as development of SWV,the air column is warmed obviously on 200hPa,but it turn partly cold,the convective instability is obvious.As well as a trough moves eastward on 500hPa,the positive vorticity enhances and extends from the lower troposphere to 300hPa and it inclines westwardly with the height.That severe precipitation happened accompanying with the formation of upper-level jet on 200hPa with the intersectional region of the southward strong wind and the northward one is located in 105°-107°E and 28°-30°N in the lower troposphere（low-level jet）.In the mean while,the water vapor is transported from southeast to northwest significantly.The characteristic of satellite cloud image appears to be MCC,the Doppler radar echo feature is mesocyclone and‘train effect’of SWV.

关 键 词：暴雨 背风槽 中-α尺度 中尺度气旋 

分 类 号：P426.62[天文地球—大气科学及气象学]