Preliminary Analysis Of The Environmental Conditions And Radar Echo Characteristics Of Hail Occurred

In order to analyze the environmental conditions of the severe hail,a statistical study on the 70 severe hailstorm cases which occur mainly in the East, Central and North China from 2002 to 2009 is conducted. The analyze result of three environment parameters(CAPE/vertical wind shear/the 0℃level height) which associate with the developing of the severe hail shows:(1) The moderate CAPE which is corresponding to the severe hail event is concentrated above 1000J/kg. (2) The severe hail events always associate with the vertical wind shear whose intensity is higher than the medium, above 2×10^-3s^-1.(3) The 0℃level height always locates at 4.0～5.0km when there are severe hail events, however,if the 0℃level height is above 5.0km, there will be few ones. In addition to the above three environment parameters, more environment parameters have been studied. The result shows:(1) The occurrence of the severe hail requires the higher potential instability energy; (2) Most of the severe hail events occur in the adequate moisture conditions, but in northwest and northeast of China, some cases appear corresponding to inadequate moisture conditions. In the end, the supplementary analysis for the 20 typical ones which are selected from the 70 severe hailstorm cases shows that supercell hailstorm is corresponding to a high storm-relative helicity.In order to analyze the radar echo characteristics of the severe hail, a statistical study on the 67 severe hailstorm cases which occur from 2002 to 2009 is conducted. The analyze result shows the relationship among the 50dBZ maximum height, the 0℃level height and hail diameter as follows: the higher of the 50dBZ maximum height,the larger diameter of the hail; With the increasing of the 0℃level height, the 50dBZ maximum height must increase in order to have the same diameter hail. However,the obvious difference also exists among the cases. After a detailed analysis on the radar echo characteristics of the 20 typical cases,the main results are as follows:All the 20 cases which are supercell hailstorm have the weak echo region (WER) and mesocyclone (M); The 50dBZ maximum height is above the -20℃level height, which means there is a strong hanging echo,and the 50dBZ always lasts a long time. The storm top divergence,S-band three-body scattering spike (TBSS) and VIL density have a great contribution to the occurrence of the severe hail. By testing the POSH and MEHS of the hail detection algorithm, the result shows as follows: The POSH has higher POD; The difference between the MEHS value and the actual hail diameter is a litter higher, however, there is still a reference value for qualitative analysis.A detailed analysis of the environmental conditions, radar echo structure and evolution characteristics of extraordinary hailstorm which occurs in Jiangsu and Anhui province during June 14 to 15 of 2005 is made based on the Doppler weather radar data, routine upper-air and surface observation, and FY-2C Satellite image, the main results are as follows: (1) The outcome of synoptic situation analysis shows: The hailfall area is in the front of the cold front ,and there is a strong potential instability energy; The upper air is dry and cold, but warm and wet air down; The adequate vapor has been supplied,and the dry line exists as a mesoscale system trigger mechanism; The dry intrusion which is observed in the water vapor image of FY-2C Satellite stimulates the production of instability energy in order to promote the development of convective weather; After analyzing the Rawinsonde observation data, the higher CAPE and vertical wind shear value appear before the severe hail events occur; Velocity vector side map shows that there is a warm advection at the lower level, and a cold advection in the top level, which increase atmosphere instability, while a high 0-3km storm-relative helicity is showed.(2) Doppler Radar data analysis result shows: With the MCS going southward,three main supercells which are mainly developed from multi-cell storm system show some typical severe hail radar echo characteristics:The strong hanging echo exists; The lower is weak echo area, while the high-level is overhanging echo and Bounded Weak Echo Region; The persistent mesocyclone is found. During the Supercell developing, the obvious storm top divergence and S-band three-body scattering spike (TBSS) have been detected,and the VIL evolvement and VIL density can effectively instruct the generation of severe hail event.