2018年5月湖南两次夜间暴雨过程的诊断分析

Diagnostic Analysis of Two Nighttime Rain-storm Processes in Hunan Province in May 2018

摘要: 本文通过对2018年5月1日和6日发生在湖南两次夜间暴雨进行分析探讨，结果表明：1) 两次过程属于两种不同的暴雨类型，“5.1”过程是湖南受584线控制在东部高空槽与南支低槽共同作用下的暴雨，“5.6”过程属于高空槽东移造成的系统性暴雨。2) 两次过程发生前，中高层均有干冷空气侵入，“5.1”过程干冷空气向低层伸展的高度明显高于“5.6”过程。3) 两次过程中850百帕以下均有较强的水汽输送通道和强的水汽通量散度辐合，中低层比湿伸展高度较厚。4) 从湿位涡MPV1看，从高层到低层两次过程均呈明显的正负正的分布特征；从湿位涡MPV2看，暴雨中心上空，有明显的MPV2正负值过渡。

Abstract: Based on the analysis and discussion of two night heavy rains in Hunan province on May 1 and 6, 2018, the results show that: 1) The two processes belong to two different rainstorm types. The “5.1” process in Hunan was controlled by 584 line, and the “5.6” process was a systematic rainstorm caused by the eastward movement of the upper trough. 2) Before the occurrence of the two processes, dry and cold air intruded into the middle and upper layers. The height of dry and cold air extending to the lower layer in “5.1” process was significantly higher than that in “5.6” process. 3) There were strong water vapor transport channels and convergence of water vapor flux divergence below 850 hPa in the two processes, and the middle and lower layers were thicker than the wet extension height. 4) From the perspective of wet potential vortex MPV1, the two processes show obvious positive and negative distribution characteristics from the upper level to the lower level. From the perspective of wet potential vortex MPV2, there is an obvious transition between positive and negative values of MPV2 over the rainstorm center.