“6.30”罕见冷涡型冰雹天气过程的环境场特征和成因分析

Analysis of Environmental Field Characteristics and Causes of “6.30” Rare Cold Vortex Hail Weather Process

2017年6月30日浙江绍兴发生了一次罕见的冰雹天气过程,通过分析表明,冰雹天气是由冷性低涡前10个纬距的暖区中对流不稳定能量释放导致;高层干冷空气的侵入,中低层的增温回暖导致了大气层结不稳定;700 hPa的西南急流提供了充足的水汽条件;地面上中尺度切变线和低涡的发展为强对流提供了动力条件;干空气侵入对于此次强对流有激发和加强作用,干侵入对应高层湿位涡的下传。K指数、CAPE、850 hPa与500 hPa温差等参数极大值出现在降雹时,而BLI、SI指数、0℃层高度在降雹时达到极小值,0~6 km垂直风切变需达到中等强度以上才有利于冰雹发生。同时还对此期间的多普勒雷达产品进行了分析,TBSS和VIL≥60 kg/m^2对于冰雹的出现有重要的指示意义,多普勒雷达产品的综合比较分析可以有效的对冰雹过程做出预测预警。

By analyzing the rare hail weather occurred in Apr 8,2008 in Shaoxing,it is found that the hail was caused by the release of convective instability in the warmer areas which led by the cold vortex from 10-wai distance behind;The invasion of dry and cold air in the upper layer and the warming of the middle and lower layers resulted in unstable atmosphere.The Southwest jet of 700 hPa provided sufficient moisture conditions;The development of mesoscale shear lines and low vortices provided dynamic conditions for strong convection.The dry air intrusion could stimulate and strengthen the strong convection,and the dry intrusion corresponded to the underpass of the wet potential vortex.The maximum values of parameters such as K index,CAPE,850 hPa and 500 hPa temperature difference appeared during the hail,while BLI,SI index,and 0°C layer height reached a minimum value during the hail,and 0~6 km vertical wind shear needed to reach medium strength above which could conducive to hail occurrence.At the same time,TBSS and VIL≥60 Kg/M2 are very important to the appearance of hail.The comprehensive comparative analysis of Doppler radar can effectively predict and forewarn the hail process.