一次低涡强暴雨的雷达回波特征

Characteristics of New-Generation Doppler Weather Radar Echoes for a Severe Vortex Rainstorm

利用大气环流背景及物理量客观诊断和西峰新一代多普勒天气雷达回波资料,对2007年7月24日河套深厚低涡造成的甘肃环县短时强暴雨过程进行了分析,结果得到：河套低涡在铅直剖面上对应有深厚的正涡度场分布;强暴雨前天气雷达强度回波反射率因子大于等于50 dBz,随高度无明显＂跃增＂,回波强中心在0℃层附近;径向速度回波的水平辐合和大于等于±20 m/s的速度中心对在2~7 km高度上活跃;云顶高度＂跃升＂变化显著;垂直液态水含量大于等于45 kg.m-2大值中心面积迅速扩大,对监测预警短时强暴雨天气和实施人影防雹作业,具有一定指示意义。

On the basis of the atmospheric circulation background and the objective diagnosis of physical quantities with new-generation weather radar data at Xifeng,an analysis is made of the short-time severe rainstorm event,induced by the Hetao vortex,in Huanxian of Gansu Province on 24 July 2007.The results show that there existed a deep positive vorticity field corresponding to the Hetao vortex in the vertical section;the echo reflectivity factor is greater than 50 dBz before the hail storm,with the strong echo center in the vicinity of the 0 ℃ layer,and there was no obvious ＂jumping＂ feature with altitude;the high value centers of horizontal convergence on the radial velocity echo image（≥±20 m/s） were highly active in the layer of 2 to 7 km;there were significant ＂jumps＂ of cloud top heights;the area of VIL being greater than 45 kg·m-2 expanded quickly,which has indicative significance for the early-warning and monitoring of short-range severe weather and hail suppression operation.