Doppler Radar Characteristics and Cause Analysis of a Continuous Downburst in Zhejiang

SHEN Xiaoling; ZHOU Hongyuan; HUANG Yingjie; ZHAO Chiyu; JIA Anqi

doi:10.16032/j.issn.1004-4965.2024.033

Abstract：Using routine observation data,ERA5 hourly reanalysis data(0.25 °×0.25 °)and Doppler weather radars in Zhejiang Province,this paper analyzed the doppler radar characteristics and cause of the event that occurred on March 21,2020.The results showed that:(1)This process occurred under the background of strong development of the southwest jet at the middle and upper levels and the surface low-pressure trough which was a forced strong convection of the low-level warm advection.The wet layer of the whole atmosphere was shallow,the near surface inversion and the middle dry cooling layer enhanced the unstable stratification with dry and cold upper and warm and wet lower,while the strong vertical wind shear in the upper air was conducive to the formation and development of strong storms,and the surface mesoscale convergence line triggered this process under the high temperature background.(2)The downburst was caused by two multi-cell storms exhibiting"Bow Echo"characteristics,including mid-level echo overhang,bounded weak echo zone,and three-body scattering.Extreme winds occurred during the descending phase of maximum reflectivity factor altitude,storm crest height,and VIL descent in unit K0,while the maximum reflectivity factor altitude,storm crest height,and reflectivity factor kernel remained relatively stable in unit Y5.(3)The downburst above level 10 primarily occurred during the stage of strong development of vorticity advection and weak cold air intrusion in the middle layer.The disaster-causing downburst in unit K0 was mainly generated by the dragging effect of hail,while in unit Y5,it was generated by the combined dragging effect of hail and short-term heavy precipitation.