Abstract:

Based on weather observation data from ground intensive stations, observation data of Tongren Doppler radar and NCEP/NCAR reanalysis data, the weather system development, structure characteristics and forming reasons of two continuous hail processes on 19 March and 22 March 2013 in Tongren were analyzed. The results are as follows: (1) The upper dry air being superimposed on the low layer warm air resulted in unstable stratification, which was the favorable circulation background of two hail processes, meanwhile, the warm and moist air flow accumulated in the middle and low layer caused heavy rainfall. (2) Strong geopotential instability caused by cold and dry air in the mid-layer and intrusion of cold air from surface was the important environmental condition for the severe convective weathers such as hail in Tongren.(3) The K index≥38 ℃，SI≤-1 ℃，SWEAT≥310，CAPE≥300 J/kg could be used as favorable indexes for hail weather forecast, and when the vertical wind shear from ground to 400 hPa was 5 ×10-3 s-1 above, it was conducive to developing and strengthening of hailstorm system.(4) Radar echo analysis showed that the strong echo with reflectivity more than 50 dBZ developed and stretched to the height more than -20 ℃ layer, and there was weak echo region or boundary weak echo region, and the radial velocity field was often accompanied by dead wind or secondary vortex, the above mentioned were all typical characteristics of hail weather. (5)When the vertical liquid water content increased to more than 25 kg/m2, it indicated that there was a hail ocurrence, and combined the hail index, they could be used as an important reference for hail warning.

Key words:  hail, radar echo, vertical wind shear

摘要：

利用地面加密自动站观测资料、多普勒雷达观测资料以及NCEP/NCAR再分析资料，对2013年3月19日和22日连续出现在贵州铜仁的2次冰雹天气过程的中尺度系统的发展演变及结构特征等进行分析。结果表明：（1）高空槽后西北气流带动高层干冷空气南下，叠加在低层西南暖湿空气上形成不稳定层结，是冰雹发生的有利环流背景形势；（2）中层干冷空气及地面冷空气侵入造成强烈位势不稳定是铜仁发生冰雹等强对流天气的重要环境条件；（3）当K指数>38 ℃，SI指数＜-1 ℃，强天气威胁指数超临界值，CAPE>300 J/kg时极有可能发生冰雹天气；当地面至400 hPa垂直风切变>5×10-3 s^-1时，利于雹暴系统发展加强；（4）反射率因子>50 dBZ的强回波发展加强，且强回波伸展高度超过-20 ℃层高度，出现弱回波区或有界弱回波区，高强悬垂回波特征，径向速度场往往伴有逆风区或中等涡旋出现，是冰雹天气发生典型特征；（5）垂直液态水含量出现跃增达25 kg/m²以上预示有冰雹发生，同时配合冰雹指数可作为冰雹预警的一个重要参考。

关键词: 冰雹, 雷达回波, 垂直风切变