一次切变型区域短时强降水过程的特征分析

ANALYSIS OF A REGIONAL SHORT-TIME HEAVY RAINFALL PROCESS BY SHEAR LINE

利用闪电、卫星和雷达等多种观测资料对2015年7月22日20∶00至23日20∶00云南的一次切变型区域短时强降水过程进行了成因分析。结果表明:700 hPa切变线和地面辐合线是此次过程的关键影响系统,切变线为短时强降水的发生发展提供了中低层水汽辐合及对流抬升运动的维持机制,地面辐合线则为低层对流发展提供了触发机制;短时强降水主要出现在云顶亮温小于-60℃的区域及亮温梯度的大值区;地闪数量开始增加的时间要早于短时强降水发生的时间;当积云回波中反射率因子达到45 dBz以上并具明显低质心特征,且径向速度图上有明显的中尺度辐合配合时,在相同区域出现短时强降水的可能性较大。

The causes of a regional short-time heavy rainfall process by shear line were analyzed, which occurred in Yunnan Province from 20∶00 on July 22 to 20∶00 on July 23,2015,based on the observational data of lightning locators, satellites and radars.The results show that the shear line on 700 hPa and the convergence lineon the ground are the key influencing systems of this process.The shear line provided a mechanism for maintaining water vapor convergence and convective uplift in the middle layer;and the convergence line provided a triggering mechanism for the convective uplift in the lower layer.The short-time heavy rainfall events mainly occurred in the areas with cloud top brightness temperature below-60℃ and large value region of brightness temperature gradient.The number of ground lighting began to increase earlier than the short-time heavy rainfall.When the radar echo intensity reaches and exceeds 45 dBz in and has obvious low center characteristics with a meso-scale convergence of radial velocity, short-time heavy rainfall with follow in the same area.