Characteristic Analyses on 500 hPa Circulation and Doppler Radar Product of Severe Hail Weather in Hexi Corridor of Gansu

According to the data of 500 hPa circulation and the surface data from 1980 to 2006,there are two types of typical environmental background of hail weather in middle part of Hexi Corridor of Gansu.Using the Doppler radar products from 2005 to 2006,the features of the hail weather are analyzed,including the base reflectivity,mean radial velocity,cross-section of reflectivity and velocity,echo top(ET),vertically integrated liquid(VIL) and vertical wind profile,etc.At the same time,the estimation error of the hail index are analyzed in near forecasting.Results indicate that the severe hail weather is relative to the high overhang structure of squall line and suppercell,the ET and VIL are well corresponding to the intensities and the time of hail strengthening or disappearing.The hail size calculated by using the strong hail index is partial to greatly,it main is because the height of 0℃ layer and-20℃ layers will be changed with the various months.