云贵高原东北部一次罕见冰雹超级单体结构特征与发展分析

Structural Characteristics and Developmental Analysis of the RareHail Supercell in the Northeast Yunnan-Guizhou Plateau

利用常规高空探测、分钟级自动气象站观测、雷达探测和ERA-Interim再分析资料,以及WRF数值模式模拟结果,对2020年5月4日发生在云贵高原东北部的罕见大冰雹(直径70 mm,突破目前贵州可查询的有气象记录以来的冰雹历史记录)过程进行综合分析,探讨了冰雹过程影响天气系统的三维结构特征和发展机制。结果表明,此次罕见大冰雹天气发生在高空槽前暖区,较高的CAPE和合适的湿球温度0℃层高度等有利的环境条件背景下;影响天气系统为中-γ尺度孤立对流系统的超级单体风暴,该风暴在多普勒天气雷达上表现为经典超级单体风暴特征,出现高达105 kg·m-2垂直累积液态水含量(Vertically Integrated Liquid,VIL);地面辐合线的激发和小涡旋的发展是超级单体风暴形成的触发原因;近地面冷池是超级单体风暴发展和增强的主要促进因素。数值模拟的结果表明,超级单体到达羊桥上空迅速增强,上升运动超过15 m·s-1,云内出现深厚的涡度对,正涡度带(最大值达4×10-3 s-1)同强上升运动相对应,冰雹增长层存在丰富的水凝物含量,均对超级单体风暴的剧烈发展和冰雹的增长起关键作用。

Using conventional high-altitude detection,automatic weather station observations,radar detection and ERA-Interim Reanalysis,and the numerical simulation model on May 4,2020,in the northeast of Yunnan-Guizhou plateau rare large hailstones(70 mm diameter,the breakthrough at present since the record of Guizhou can query the hail history)process is analyzed and simulated.The analysis shows that this rare hail weather occurred in the background of favorable environmental conditions,such as high CAPE and appropriate wet-bulb temperature 0℃layer height,the warm zone before an upper trough.The synoptic system is a meso-γisolated convective system called supercell storm.The storm is a classic supercell storm on the Doppler weather radar,and the vertical accumulated liquid water content(VIL)up to 105 kg·m-2 is an important reason for the formation of this rare large hail.The convergence line excitation and the development of small vortices are the trigger causes of supercell storm formation.The near surface cold pool is the main factor to promote the development and enhancement of supercell.The results of numerical simulation show that the supercell quickly strengthen when it reach Yangqiao,vertical rising movement of more than 15 m·s-1.Deep vorticity pairs appear in the cloud,and the positive vorticity band corresponds to the rising movement.The hailstone growth layer has a large content,which plays a key role in the development of supercell storms and the growth of hail.