初夏孟湾风暴造成云南连续性强降水的中尺度分析

MESOSCALE ANALYSIS OF YUNNAN SUCCESSIVE HEAVY PRECIPITATION CAUSED BY STORMS OVER THE BAY OF BENGAL IN THE EARLY SUMMER

关键词:  孟加拉湾  风暴  强降水  中尺度分析

Key words:  the Bay of Bengal  storm  heavy precipitation  mesoscale analysis

摘要:

利用常规气象资料、物理量场、卫星云图和多普勒雷达资料对孟湾风暴影响下云南初夏出现的4次连续性强降水天气过程的中尺度特征及其环流背景条件进行了分析。结果表明:孟湾风暴在孟加拉湾海域生成后,生命史一般为2～3天,风暴云团云顶亮温低于-65℃;孟湾风暴以分裂中尺度对流云团、外围云系以及登陆减弱的本身沿孟湾槽前和副高外围的西南气流北上影响云南;高原低涡切变、辐合通道和西南风速的辐合为孟湾风暴东北上云南提供了有利的环流背景和动力条件;孟湾风暴影响云南在多普勒雷达回波上存在许多共同的特征,往往是絮状回波产生连续性降水

Abstract:

By using regular meteorological data,physical quantity fields,satellite imagery and Doppler radar echo data,we analyze the mesoscale features and the conditions of 4 successive heavy precipitation processes in Yunnan caused by storms over the Bay of Bengal in the early Summer.The results show that the life of the storm over the Bay of Bengal is 2 or 3 days and the cloud-top temperature of the storm is always below –65 ℃.Storms over the Bay of Bengal affect Yunnan by mesoscale convective cloud clusters,peripheral cloud bands or weaken themselves as they are moving to the Northeast.The Tibetan shear lines and vortexes,NE-SW convergence channels and southwest wind convergence supply favorable circulation background and dynamical conditions.There are many common features in Dopplar radar echoes.They are usually about 35～45 dBZ strong and move to the east and produce successive precipitation in Yunnan and the mesoscale features of southwest jet and wind rotating clockwise with altitude not only are favorable for storms over the Bay of Bengal to transport warm and humid air current over to the north,but also are favorable to convection development.