2012年7月4日河南大暴雨过程的短时强降水成因分析

利用常规观测资料、雷达和区域自动站资料及NCEP再分析资料，对2012年7月4-5日河南黄淮大暴雨过程的成因进行分析。结果表明：大暴雨过程发生于副热带高压加强西伸北抬的背景下，由两种性质的强降水构成，一种强降水持续时间短但强度大，而另一种持续时间长但强度相对弱。低涡切变是此次暴雨过程的主要影响系统，低涡东南象限的低空西南急流不仅为暴雨过程提供了充分的水汽、能量条件，而且为强降水的发生提供了动力辐合条件。冷空气及地面辐合线对强降水的形成起触发作用。午后强降水持续时间短、强度大，主要是由暖切变附近迅速发展的伴有中气旋的强降水对流单体造成的，中气旋活动频繁，最强降水位于“人”字形雨带交叉点处；夜间持续时间长、强度相对弱的强降水由强降水回波“列车效应”造成，中气旋不活跃，但地形对夜间降水有促进作用。

Cause Analysis of a Short-time Strong Rainfall of the Rainstorm Process on July 4, 2012 in Henan Province

Regular observational data, radar and AWS data as well as NCEP reanalysis data are used to analyze the cause of rainstorm between the Yellow River and the Huaihe River from 4 to 5 July 2012. The result shows that strengthening and northwestward motion of subtropical high is the background of the process, consisting of two kinds of strong rainfall, one is short duration and strong rainfall intensi- ty, the other is long duration and relatively weak. The low vortex shear system are the main influence sys- tems in this process. The southwest jet stream in the lower level provides both the adequate water vapor and energy and the powerful dynamic convergence conditions. Cold air and ground convergence line are the trigger mechanism for this process. The strong rainfall with short duration and strong intensity in the afternoon is caused by the strong rainfall convective cells which rapidly developed around the warm shear. There are frequent activities of mesocyclone around the convective cells, and the most intensive rainfall locates in the crossing point of the herringbone rain belt. While the another short-time strong rainfall with long duration and weak rainfall intensity in the night is caused by the ＂train effect＂ of strong echo, and the mesocyclone was not active. In addition, the terrain probably promotes the rainfall at night.