2012年早春广西高架雷暴冰雹天气过程分析

利用常规观测资料和雷达资料,对2012年早春广西高架强雷暴冰雹天气过程进行分析,得出以下结论:(1)冰雹伴随雷暴发生在地面锋后约1000 km,边界层为冷高压控制.850 hPa风速较小,700 hPa以上层有强急流,700～850 hPa有强的垂直风切变,500 hPa高空冷槽东移为对流的发生提供触发条件.(2)冰雹发生在850 hPa切变线南北两侧约200 km范围,等压面锋区强度大；高空槽前正负变温使700～500 hPa垂直方向温度差大,导致层结对流不稳定性加大.当500 hPa低槽移至强锋区上空时,锋面坡度变陡,上升运动加强,不稳定性增大,使得冰胚在对流层中层增长而形成冰雹.(3)风暴追踪信息显示风暴生成高度高,在垂直方向上倾斜增长;质心均在5～6 km,风暴生成后,随着时间的推移逐渐向低层发展,最大反射率以及液态含水量均不大,具有明显高架雷暴特征.

Analysis on Elevated Thunderstorm Hail in Guangxi in Early Spring of 2012

Based on conventional observational data and radar data, the elevated thunderstorm hail process in Guangxi in early spring of 2012 is analyzed. The results show that: (1) Hail accompanied by thunderstorm occurs on the surface about 1000 km away from the front, and boundary layer is controlled by cold high pressure. The smaller winds at 850 hPa, strong jet stream at 700 hPa and above layer, strong vertical wind shear between 700 hPa and 850 hPa and eastward move of cold trough at 500 hPa provide the trigger condition for the occurrence of the convection. (2) Hail occurs in the range of approximately 200 km away from the shear line at 850 hPa, where there is strong intensity of the pressure surface frontal zone. The negative variable temperature in front of the upper trough increases the temperature difference in vertical direction between 700 hPa and 500 hPa, resulting in the increase of stratification convective instability. When the trough at 500 hPa moves up to the air above the frontal zone, the frontal slope becomes steep, and the upward movement strengthens while the instability increases. All of these make the ice embryo grow in the troposphere and form hail. (3) The storm tracking information displays that storms are generated in high altitudes, and the centroids are 5-6 km high. After the storm is generated, the centroids gradually develop to lower layer with time going. The maximum reflectivity and liquid water content are not large, showing the significant characteristics of the elevated thunderstorms.