湖南一次持续性极端暴雨过程成因分析

Cause analysis of a persistent Extreme Rainstorm in Hunan

利用常规观测、自动站加密雨量资料、NCEP再分析资料,对2017年6月22日~7月2日湖南持续性暴雨过程进行分析。结果表明:暴雨过程可分为强、弱、强三阶段。暴雨是由500hPa北支槽横转竖引导低层冷空气南下,与持续强劲的西南暖湿气流交汇和低层切变线共同触发造成的。西南低空急流为暴雨产生提供了持续的辐合上升运动,急流强度和位置的变化与降雨强度和位置有一定相关性。后期副高西侧东南水汽的加入增强了水汽输送,降水量最大。

Using conventional observation data, encrypt rainfall data of automatic station,and NCEP reanalysis data, this paper analyzed the causes of the persistent heavy rainfall in Hunan Province from 22 June to 2 July, 2017. The results show that the process of the heavy rainfall can be divided into three stages： strong stage, weak stage, and strong stage. The heavy rainfall was triggered by the low-level shear line and 500 hPa north trough, which changed from horizontal to vertical, joining with the per- sistently strong southwest warm and humid air flow. The southwest low-level jet provided a continuous convergent upward mo- tion for the occurrence of heavy rain. The intensity and location of the jet were related to the intensity and location of rainfall.In the later stage, the addition of water vapor in the southeast side of the subtropical high enhanced the water vapor transport and led to the largest precipitation.