一次罕见的左移超级单体风暴的特征

Characteristic of a Rare Moving Left Supercell Storm

利用白山多普勒天气雷达、常规观测和地面加密观测资料,对2012年7月2日发生在吉林省南部的一次左移超级单体风暴进行了研究。结果发现,此次天气过程发生在深厚东北冷涡的东南象限、超强高空急流核附近的北侧,且低空风垂直切变不强、对流有效位能不大;低空有较强的暖平流,并存在一个西南—东北走向的风切变区;低空辐合、高空辐散、位于露点锋附近以及高空急流核的存在为有利于的对流发展的重要因素。在风暴发生发展过程中,始终有一个中-β尺度反气旋环流(尺度为120 km)相伴随,其旋转半径由高到低逐渐增加并在东南偏南方向被拉伸为椭圆型结构,风暴发生在该环流的西北象限的西南偏南气流之中,并具有钩状回波、弱回波区、反中气旋等超级单体所具有的特征。反中气旋出现在对流风暴发展的旺盛期,旋转半径从低层到高层逐渐增加。在风暴经过地区出现了冰雹、强降温、瞬时大风等天气现象和气象灾害。

A study of a left moving supercell storm which occurred in the southern part of Jilin Province on July 2 2012 was made based on the Baishan Doppler weather radar data,routine upper air observation,and intensive automatic weather station observation. The results show that this weather process occurred in the deep northeast cold vortex southeast quadrant and near the north side of the super strong high-altitude jet cores,low-level vertical wind shear was not strong and convective available potential energy was not large then. There was a strong warm advection in low level and a wind shear area from southwest to northeast. Low-level convergence,upper-level divergence,near the dew point front and upper-level jet cores were all conducive to convective development. There was always a meso-β-scale（ about 120 km） anti-cyclonic circulation when the storm developed,its rotating radius increased gradually from upper to low level and it was stretched into an oval structure in SSE direction,and the storm occurred in the SSW airflow in the northwest quadrant of the circulation,and showed a hook echo,weak echo region,anti meso cyclone and other characteristics of supercell. Anti-meso-cyclone appeared in the strong developing period of the storm,and its gyration radius gradually increased from low to high layer. Hail occurred in front of the strongest inflow and strongest period of the storm,and strong cooling and instantaneous gale disasters weather happened when the storm passed by.