西行低涡特征及其对“21.7”河南暴雨影响分析

Characteristics of Westward Vortex and its Impact on“21.7”Henan Rainstorm

2021年7月河南出现极端暴雨,黄淮地区存在一个自东向西移动的低涡,是降水过程发展增强的主要影响系统。针对低涡的研究主要集中于自西向东的移动路径,很少考虑西行低涡的机制及特征。利用地面常规气象资料、区域气象站及雷达等非常规观测资料、ERA5再分析资料,对“21.7”暴雨的大气环流形势、西行低涡移动路径、各层系统配置及低涡西行原因进行特征分析,并从水汽、热力、动力及对流触发等方面分析西行低涡对“21.7”暴雨的影响,结果表明:(1)“21.7”河南暴雨期间大气环流形势稳定,黄淮地区为典型的“鞍型场”,西行低涡移动路径为先向西南后向西北。(2)西行低涡各层系统配置复杂,低涡东侧副高及台风“烟花”西进使低涡附近偏东急流加强,低涡自东向西移动。(3)西行低涡水汽条件充沛、动力条件旺盛、热力条件充足,低涡与低层切变线、地面辐合线共同作用,使对流触发条件增强。

In July 2021,an extreme rainstorm occurred in Henan Province,and there was a vortex moving from east to west in the Huanghuai area,which was the main influencing system for the development and enhancement of the precipitation process.Although research on this vortex mainly focuses on its eastward movement,little attention has been paid to the mechanism and characteristics of its westward movement.Based on the|conventional meteorological data,regional meteorological stations,radar,and other unconventional observation data,ERA5 reanalysis data,the characteristics of the atmospheric circulation situation,the moving path of the westward vortex,the lconfiguration of each layer system and the reasons for the westward movement of the vortex were analyzed,and the influence of the westward vortex on the“21.7”rainstorm was analyzed from the aspects of water vapor,heat,power and convection triggering.The results show that:(1)During the rainstorm of“21.7”in Henan,the atmospheric circulation situation was stable,the Huang-Huai area was a typical“saddle field”,and the moving path of the westward vortex was from southwest to northwest.(2)The subtropical high on the east side of the vortex and the westward advance of typhoon“fireworks”strengthen the easterly jet near the vortex,and the vortex moves from east to west.(3)The westerly vortex has abundant water vapor conditions,strong dynamic conditions and sufficient thermal conditions.The vortex interacts with the low-level shear line and the ground convergence line to enhance the convective triggering conditions.