Analysis On Doppler Radar Echo Feature And The Formation Mechanism Of Hail Clouds In Spring And Summer In Yunnan Province

By using Doppler radar data and serial data of hail clouds in Dali,Pu'er,Dehong,Lijiang,Kunming and Wenshan,in Yunnan Province,Doppler radar echo characteristics of all typical hail clouds during 2014-2017 in these areas were analyzed.Then typical hail cloud were selected for case analysis,including the evolution law and feature analysis of the radar echo of hail clouds.Next,different indicators were selected which have good correlation with the hail cloud in various parts of Yunnan Province,multi-factor probability method was used to combine with other parameters of the echo,so that different discriminant criteria of hail clouds were established for each place in Yunnan Province.Finally,by using Doppler echo data the features of hail clouds in spring and summer were analyzed.This paper provided effective reference information for hail weather forecasting and hail suppression so as to reduce the meteorological disasters and social impacts caused by hail clouds in Yunnan province.The main conclusions are as follows:1)For single-cell hail cloud:the statistical characteristics are basically consistent with the analysis results of individual cases:"v" shaped notch echo,head wind area and other characteristics are obvious;There are fewer cases and longer average hail time in spring,and there are more typical features of single-cell hailstorm in summer.2)For supercell hailstorm:the statistical characteristics are basically consistent with the analysis results of individual cases:hooked echo,"v"notch echo,false cusp echo,hanging echo,mesocyclone and other characteristics are obvious;In summer,supercell hailstorm often has obvious characteristics of the low-level convergence and the upper level divergence.3)For multi-cell hailstorm:the statistical characteristics are basically consistent with the analysis results of individual cases:v-shaped notch echo,bow echo,false cusp echo,bounded weak echo region,and head wind area are obvious;In summer,head wind area is a usual feature.4)Hail mainly occurred in spring and summer in Yunnan province,and the single-cell hail cloud has the most obvious seasonal changes for all kinds of indicators and from 2014 to 2017.characteristics.However,there are no typical individual cases of squall line in summer5)Compared to single-cell hail cloud,supercell hailstorm usually has the characteristics of hook echo,bounded weak echo region,overhanging echo and mesocyclone and larger echo intensity,longer hail fallout time6)Squall line has the similar statistical characteristics to multi-cell hail cloud Compared to multi-cell hail cloud,supercell hailstorm usually has longer hail fallout time and the characteristics of gale.Head wind area is a conjugate system to mesoscale convergence and divergence when it happens in multi-cell hail cloud,but it is also a conjugate system to mesoscale cyclone and anticyclone when it happens in squall line.7)The convective development is the most vigorous in Pu'er and Wenshan8)The comprehensive probability method is effective for judging the test results of hail clouds for different areas,but considering the problems of data limitation and weight,it needs to be improved.