Analysis of a Wet Downburst in the Liaodong Peninsula

Abstract

On September 11， 2020， severe convective weather occurred in the southern part of Liaodong Peninsula， and wet downbursts appeared.The maximum surface wind gust at Dalian Jinzhou Desheng station reached 21.7 m·s-1.By using conventional observation data， Dalian Doppler radar data， ERA5 data and high-resolution mesoscale simulation data， the circulation background， convective environment and echo characteristics of this wet downburst was analyzed.The results show as follow： （1）the major synoptic system is shear line made up of southwest and southeast winds located to the east of upper-level cold vortex transformed by north-moving tropical cyclone.The mechanisms of convective initiation are surface convergence line and low-level jet.Coupling upper-level divergence enhances initial connection development.The convection system moved westward and landed on the frontal zone between the ground cold pool and the east warm air， and the convergence lifting effect increased， promoting higher organization and more severe of the convection system.（2）The highly warm and moist surrounding air and the instability are favorable conditions for convection.Before convection occurred， the sounding shows dry air overlapping moist air and "V" pattern.The lifting condensation level decreases distinctly.During the wet downburst， radar radial velocity shows mid-altitude radial convergence（MARC）， low-level divergence.Before and after the gale， high and low elevations all exhibits more than 45 dBZ reflectivity notch.The high reflectivity notch at high elevation appears prior to that at low elevation.Monitoring the changes of the high elevation reflectivity contributes to the early warning of wet downburst.

Keywords

• wet downburst
• low-level jet
• cold pool
• high reflectivity notch