"06.7"郧西暴雨天气的成因分析

利用常规气象资料和卫星云图资料,采用天气学诊断方法,从大尺度环流背景、天气系统、物理量场、对流云团演变特征等方面,分析了2006年7月3～4日出现在湖北郧西的一次暴雨天气过程的成因。结果表明,此次暴雨是在副热带高压减弱东退形势下产生的;700 hPa和850 hPa的冷槽、切变线是此次强降水的主要影响系统,暴雨区位于700 hPa切变线右侧、850 hPa切变线附近;暴雨区上空存在明显正涡度柱,低层辐合与中高层辐散形成抽吸作用,为暴雨过程发生发展提供了动力条件;存在于孟加拉湾至我国西南地区的水汽通道为暴雨过程提供了必需的水汽;整个暴雨过程都伴随着中尺度对流云团的初生、发展、合并和减弱,降水主要由发展型对流云团造成。

Causality Analysis for the "06.7" Heavy Rainstorm in Yunxi

By using the synoptic diagnostic method,the causes of heavy rainfall occurred in Yunxi on 3-4 July of 2006 are analyzed on circiulation background,synoptic system physical field and evolutional feathers of convection cloud cluster with conventional observations and satellite data.The results show that the eastward retreat of the western Pacific subtropical high provided the very favorable large-scale circulation background for the rainfall.The main influence systems of the rainfall are the cold trough and the shear line at 700 and 850 hPa.The rainfall area located at the right of shear line at 700 hPa,nearby shear line at 850 hPa.The ascending movement,positive vorticity and pumping over the rainfall area are its dynamical conditions.Sufficient water vapour are transported to the heavy rainfall area with the channel existed from Bay of Bengal to the southwest regions of China.The entire rainfall is mainly caused by the genesis and development of mesoscale convective cloud clusters.