鄂北一次超级对流单体的双偏振雷达特征分析

Dual-polarization Radar Characteristics Analysis of a Supercell in Northern Hubei

利用湖北省随州市S波段双偏振雷达资料及常规观测资料,对2020年5月4日鄂北随州出现的超级单体风暴进行分析。结果发现:(1)在有利天气背景作用下,形成了上干冷下暖湿的垂直层结、0~6 km中等强度垂直风切变以及地面辐合线,为强风暴的发生发展提供环境条件和触发条件。(2)超级单体发展过程中,观测到前侧"V"形入流缺口、中气旋、弱回波穹隆、悬垂回波、钩状回波等特征,且风暴顶高度、风暴质心高度、最大水平反射率因子高度以及垂直累积液态含水量等风暴参数均呈先升后降趋势。(3)超级单体的发展和成熟阶段,在0℃层以下的低层,于前侧下沉气流西侧的水平反射率因子大梯度区观测到浅薄的差分反射率因子Z_(dr)大值区,即Z_(dr)弧;(4)超级单体的初始阶段、发展阶段以及成熟阶段,在0℃层之上的中层,观测到强上升气流的正温度扰动使冰相粒子在附近融化而形成的Z_(dr)环形大值区和相关系数环形小值区。(5)垂直方向上,在超级单体的初始阶段、发展阶段以及成熟阶段均观测到Z_(dr)柱和差分相位常数K_(dp)柱。Z_(dr)柱与弱回波穹隆区位置对应较好,其不同时期特征反映了上升气流强的变化;K_(dp)柱的变化反映了超级单体中含有大量液态水滴区域的变化。

The Suizhou S-band dual-polarization radar data and conventional observations are used to analyze a supercell in the northern Hubei on 4 May 2020. The results show that:(1) The favourable weather conditions provided the vertical stratification of dry and cold in the upper part and warm and wet in the lower part, moderate-intensity vertical wind shear in 0 to 6 km and the surface convergence line. They provided the environmental conditions and trigger conditions for the strong storms.(2) During the supercell development, the front “V” inflow gap, mesocyclone, weak echo dome, drape echo and hook echo were observed. Moreover, the storm top, the centre of storm mass, the height of maximum horizontal reflectivity factor and the VIL showed the trend of first rising and then falling.(3) During the development and maturity of the supercell, a shallow region of high differential reflectivity was found along the large gradient region on the west of forward-flank downdraft below 0 ℃ which was termed as Z_(dr)arc.(4) During the beginning, development and maturity stages of the supercell, a mid-level circular ring of enhanced Z_(dr)and depressed R was found above the 0 ℃ layer, formed by the melting of ice particles due to the positive temperature disturbance strong updraft.(5) In the vertical direction, the Z_(dr)and K_(dp)columns were observed in the supercell’s beginning, development, and maturity stages. The position of the Z_(dr)column was consistent with a weak echo dome, and its characteristics in different periods reflected the change of updraft intensity;the change of the K_(dp)column demonstrated the change of liquid droplet region in the supercell.