甘肃省河东地区一次暴雨天气特征以及成因分析

The Weather Characteristics and Cause Analysis of a Heavy Rain in Hedong Area of Gansu Province

摘要: 利用逐小时ERA5再分析资料和常规气象资料，从环流形势、中尺度特征、物理量诊断等方面，对2019年8月2日甘肃省河东地区一次区域性暴雨天气过程的特征和成因进行分析。结果表明：这是一次上干下湿的环境条件下，由低层切变线触发而产生的一次暴雨天气过程；暴雨落区与相对湿度大于90%的区域及能量锋的位置相对应；台风“韦帕”外围的暖湿气流为此次暴雨过程提供了充沛的水汽；地形的抬升作用进一步增强了上升运动，促进对流发展；风切变导致不稳定能量的释放是造成局地强降水的重要原因，湿位涡分量等值线密集区对降水落区具有一定的指示意义。

Abstract: Based on ERA5 reanalysis data and conventional meteorological data, the characteristics and causes of a regional rainstorm weather process which occurred in East of the Yellow River, Gansu Province on August 2, 2019 were analyzed from the aspects of circulation situation, mesoscale characteristics, and physical quantity. The results show that the rainstorm weather process is triggered by the low-level shear under the environmental conditions of upper dry and wet lower. The rainstorm area corresponds to the area where the relative humidity is greater than 90% and the energy front formed. The warm humid air around the typhoon “Weipa” provided abundant water vapor for the rainstorm process. The uplift caused by terrain further enhanced the upward movement and promoted the development of convection. The release of unstable energy caused by wind shear is an important cause of strong local precipitation, and the dense area of the wet potential vorticity component is an indicator of the precipitation area.