一次川东大暴雨过程的中尺度分析

MESOSCALE ANALYSES OF A SICHUAN HEAVY RAINFALL

利用观测资料和MM5中尺度非静力模式产生的客观分析资料,分析了2004年9月3～5日出现在川东地区大暴雨过程的大尺度环流特征和主要的中尺度天气系统及其结构.分析表明:中纬度低压槽的东移与西伸加强的副热带高压在青藏高原北部地区形成了有利于高原切变线和西南低涡生成发展的环流条件;西南低涡东侧的暖式切变线是对流活动最活跃的区域,强降水主要出现在暖式切变线上;西南低涡是一个主要出现在对流层中低层的涡旋系统,与大暴雨区相对应的整层强上升运动是低涡切变线南北两侧的正反向垂直环流共同作用的结果.

A diagnostic study on a severe rainfall occurred over the northeast of Sichuan province in 3-5 September 2004 is undertaken with the rainfall characteristics, large scale circulations and the meso-scale synoptic systems presented. Results show that wind shear at the east part of Tibetan Plateau and southwest vortex at the lower level in the basin of Sichuan play the key role in the occurrence of the heavy rainfall. The convective activities and the heavy rain mainly occurrs on the sharp wind shear which locates over the east of the vortex center. The very strong vertical velocity is detected which is sustainable by two second vertical circulations located respectively at the north and south of the southeast vortex.