一次左移反气旋超级单体的观测分析

2006年8月10日在甘肃河西走廊山丹县境内发生了一次左移（反气旋）超级单体灾害性天气,在其2 h生命史期间,山丹县境内降了最大直径2 cm的冰雹。从其发生、发展的天气尺度环境条件、多普勒天气雷达反射率因子、径向速度以及风矢端图、相对风暴螺旋度等角度,揭示了左移超级单体的特征,并利用ID方法对这次左移超级单体的移动路径进行了预报。结果表明：风矢端图上,在1.2~4.5 km高度层,左移超级单体的垂直风切变矢量呈反时针旋转;左移超级单体在发展阶段,0~3 km内相对风暴螺旋度为负值;通过比较,ID方法预报的超级单体位置比现行PUP产品中的SCIT算法绝对误差要小。

Observation and Analysis of a Left-moving Supercell

The hail weather with the maximum diameter of 2 cm triggered by a left- moving（ anticyclone） supercell occurred in Shandan of Hexi Corridor on 10 August 2006,and lasted for 2 hours. The characteristics of the left- moving supercell were revealed by analyzing synoptic scale environment condition,reflectivity factor,radial velocity,hodogragh and storm relative helicity of weather radar.At the same time,the positions of the left- moving supercell were forecasted by using ID method. Results indicated that the hodogragh curve of the left- moving supercell spined counterclockwise over 1. 2- 4. 5 km layer and the values of storm relative helicity（ SRH）for the left- moving supercell were negative over 0- 3 km layer. By comparison,the absolute errors of the supercell position forecasted by using ID method were smaller than that by using SCIT,but the forecasted azimuth errors of the former were greater than the latter.