一次高原低涡切变东移引发的持续性特大暴雨过程分析

Analysis of a Sustained Torrential Rainstorm Events in Sichuan Basin Induced by Plateau Vortex Moving Eastward

利用常规观测的地面和高空资料、地面加密自动站资料、美国国家环境预测中心（NCEP）提供的一天4次1°×1°再分析资料以及FY2E卫星TBB资料,对2013年7月15-19日高原低涡切变东移诱发的四川盆地特大暴雨过程进行了诊断分析。结果表明：强降水落区发生在副高边缘西北侧的不稳定区域内,低层和地面冷空气扩散南下是触发特大暴雨发生的关键因素。强降水主要出现在MCS系统发展和成熟阶段,最大降水出现在MCS中心最冷云顶面积达到最大的时候。中低层水平湿Z-螺旋度负值区域分布与相应时刻的降水落区和天气系统有较好的对应关系。垂直分布上,暴雨区低层正涡度、水汽辐合旋转上升与高层负涡度、辐散相配合,是触发暴雨的有利动力机制。

Using the conventional observation data,precipitation data from automatic stations,NCEP reanalysis data（ 1°× 1°） from NCEP / NCAR center and FY2 E satellite TBB,a case of heavy rainstorm in Sichuan basin caused by plateau vortex shear moving eastward from 15 to 19 July 2013 was analyzed. Results are as follows： The heavy rainfall occurs on the edge of northwest of the subtropical high,which is the unstable region,and the proliferation of the low- level cold air moving southward is the key factor in triggering heavy rainfall occurs. The strongest intensity of heavy rainstorm appears in the mature stage of development of the MCS system,and so dose the 1h maximum precipitation when the coldest cloud increases to the top size.The horizontal distribution of negative wet z- helicity at low- level correspond well with the heavy rainfall center of the same period of time. In the vertical distribution of the rainfall area,the favorable dynamic structure of the positive vorticity with water vapor convergence rotation in the low- level and negative vorticity with moisture divergence rotation in the high- level contribute to trigger the torrential rain.