东风波引发的湖南南部强暴雨过程分析

Analysis of Heavy Rainfall in Southern Hunan Caused by Easterly Wave

利用常规观测资料、ERA5再分析资料及永州多普勒雷达资料等对2016年8月12—13日湖南南部的东风波暴雨过程进行综合分析。结果表明:这次深厚东风波暴雨过程处于南亚高压由西部型向东部型转换的过渡阶段,副热带高压控制我国中东部,西南季风卷入到副热带高压南侧强盛偏东风波动中,诱生出低涡,使得垂直风切变加大,东风波系统得以较长时间维持;主要降雨区位于诱生低涡经过的区域和东风波槽前东北气流区,低涡西侧的能量锋区及东风波槽前θ_(se)大值区的出现均对强雨区的预报有一定的指示作用,当槽前正涡度平流中心与低层θ_(se)大值区重叠时,降水强度明显增大;强雨区与湘南地区特殊地形密切相关,暖湿气流与山脉走向夹角大,使得降水增幅明显。

Based on conventional observation data,ERA5 reanalysis data and Yongzhou Doppler radar data,the heavy rainfall occurring in Southern Hunan Province from 12 to 13 August 2016,which was affected by easterly wave,was analyzed.The results show that the heavy rainfall process occurred in the period when the 200 h Pa South Asian high was converting from the western type to the eastern type,and the central and eastern China were controlled by the Western Pacific subtropical high(WPSH).The mesoscale low vortex was induced by the southwest monsoon and easterly wave on the south side of WPSH,and it was the low vortex that increased the vertical wind shear and made the easterly wave maintaining for a long period of time.The main rainfall area was located in the zone where the mesoscale low vortex passed through.It was also within the range of the northeast wind in front of the easterly wave trough.Both the frontal zone of energy on the west side of the vortex and the large value region ofθ_(se)(equivalent potential temperature)in front of the easterly wave indicate the occurrence of rainstorm in a certain area.The precipitation intensity will increase significantly when the center area of the positive vorticity advection in front of the easterly wave overlaps with the lowlevelθ_(se) large value area.There is high correlation between the rainstorm area and the special terrain of southern Hunan.The large angle between the alignment of mountain and the warm moist flow makes the precipitation increase significantly.