秋季川东北一次西南低涡大暴雨分析

利用高空实况实时分析场、FY-2ETBB以及地面加密自动站实况资料,对2014年9月13~14日发生在四川盆地东北部的大暴雨过程进行了分析。结果表明:(1)川东北大暴雨天气过程形成的关键是较为深厚的西南低涡长时间稳定少动,大暴雨区位于北支西风急流南侧和南支东风显著风速带北侧辐散上升运动区的重叠区内,稳定的东高西低的环流形势是这次暴雨发生的大尺度环流特征,地面风向切变的形成对暴雨的产生具有一定的指示意义;(2)在长生命史、稳定的西南低涡内存在多个MCS对流云团的连续生消,MCS云团冷云中心都呈近圆形,移动缓慢,云团发展到成熟阶段,冷云中心TBB值低于-72℃,在减弱的冷云罩中有中小尺度雨团的生成、畸变、分裂的现象发生,在每个强降雨时段内又存在着两个或多个短时强降水峰值;(3)在此次降水过程中重庆沙坪坝站对于广安13日的强降水更具有指示意义,3个时次中沙坪坝站露点曲线和层结曲线之间形成低层暖湿,中高层干冷,有利于强对流天气发生的“喇叭口”形状。 

The Features of a Severe Torrential Rain Caused by Southwest Vortex in Northeast Sichuan Basin in Autumn

Based on the intensive meteorological observation stations data,sounding data,and FY-2E Satellite cloud images,the persistent and severe rainstorm process which occurred in northeast Sichuan Basin from 13 to 14 September 2014 was analyzed. The results show that:(1) This rainfall occurred in the stable circulation of eastern Asian,with East high and West low,northeast of Sichuan Basin located in southerly side of upper-level westerly jet and northerly side of upper-level easterly jet of branch,it is conducive to development. The key of northeast Sichuan heavy rainstorm process is the maintenance of the SW vortex at Sichuan Basin long time. The formation of the surface wind direction shear has certain significance to the rainstorm.(2) the extremely heavy rainstorm is caused by mesoscale convective systems(MCS),which continual appearing and disappearing in the Southwest Vortex weather system. MCS cloud development to the mature stage,move slowing,cold cloud center TBB values below 72 degrees. There are many mesoscale rain cluster,and there are two or more short-term strong precipitation peaks in each heavy rainfall period.(3) In the precipitation process,Shapingba station sounding data is more reference value for this strong precipitation at 13,One of the features revealed is that a V-shape separation occurs between the stratification curve and the dew point profiles,this shape is benefit to severe convective weather.