Based on the application of Lanzhou Doppler radar products, the theory pattern of vertically integrated liquid water content (VIL) which is one of radar physical quantity products was introduced in this article. Several issues was brought forward from some aspects of the influence of radar detecting range and height, reflectivity intensity on the calculation of VIL, as well as VIL changed with season variation, so as to supply some references to distinguish severe convective weather based on VIL.

The causes of a heavy rain with hails and thunderstorm which occurred in the east part of Gansu province on July 4th 2004，were analyzed from three aspects of the synoptic environment，physical quantity field and the characteristics of Doppler radar echoes. Results show that it was a typical northwest flow pattern at the level of 500 hPa，and the intensity of cold advection increasing with height resulted in instability energy accumulation，the dry and cold air touching off the energy front from the east side of Tibet plateau to the middle part of Gansu province led to the strong convection. The evolution of radar echoes showed that the hailstones came from multi - cell storms and the meso - γ scale cyclone could be identified by the radial velocity products of Doppler radar

According to the synoptic background and the evolution characteristics of radar echoes of a strong single hail event occurred in Yongdeng county of Uansu Province on July 8，2003，the jumping change of echo height，intensity and liquid water content，and the special structure features of the strong single hail were analyzed in this paper. 'hhc results show that the range and extension height of strong reflectivity area on vertical section arc important to hailstorm development.  While the strong reflectivity area is corresponding to bunbant  watea area In cloud，and only water content accumulating area being in the cooled 4km,region in the cloud can t0  abundant he benefit to hail development.  <)nec the echo intensity reached 55 dBz and its height was above hail falls immediately. 'hhe strong single hail with special structure developed very strongly.  Above conclusions
arc nificant to hail monitoring and prcwarning.