广东省中部一次强降水超级单体的双偏振雷达观测分析

Analysis of a High Precipitation Supercell Based on Dual Polarization Radar Observations in Central Guangdong Province

为揭示广东省强降水超级单体风暴的偏振特征及其动力结构,利用广州市双偏振雷达数据及常规气象观测资料,对2020年6月7日造成广东省中部一次特大暴雨过程的强降水超级单体风暴进行分析研究,结果表明:(1)此次强降水过程中切变线南侧西南低空急流提供了充足的水汽供应和不稳定能量,中层多波动短波槽带来的干冷空气增大层结不稳定,地面辐合线有利于触发对流的发生发展。强降水前超低空偏南气流加强并向高层传播,随低空急流的形成和扩展,降水强度明显增强。(2)过程期间佛山市和清远市不断有回波生成发展并在东移过程中合并增强,发展为强降水超级单体。在超级单体的低层,相关系数小值区可用于指示低层上升气流的位置与有界弱回波区和钩状回波位置,而中气旋形成前的差分反射率(ZDR)环、相关系数(CC)环则指示中层上升气流的位置,以及涡旋发展成中气旋的潜势。强反射率因子值差异不大时,差分相移率(KDP)值越大,说明降水越强。

A severe precipitation supercell accompanying extremely heavy rainfall in central Guangdong Province on 7 June 2020 is analyzed based on observations of dual polarization radar and conventional observations in Guangzhou so as to reveal the polarimetric signatures and dynamic characteristics of this severe precipitation supercell.The results show that:(1)During the extremely heavy rainfall process,the southwest low-level jet on the south side of the shear line provided sufficient water vapor and unstable energy,the middle-level multi-wave shortwave trough brought dry and cold air enhancing the stratification instability,and the ground convergence line triggered the occurrence and development of the severe convection.Before the severe rainfall,the ultra-low-level southerly airflow was strengthened propagating to the upper layers.With the formation and expansion of the low-level jet,the precipitation intensity increased significantly.(2)Precipitation echoes continued to generate and develop over Foshan City and Qingyuan City,and then merged and strengthened in the process of eastward movement,developing into a severe precipitation supercell.In the lower layer of the supercell,the area of decreased correlation coefficient can be used to indicate the positions of the updraft in the lower layer,the bounded weak echo zone and the hook echo,while the differential reflectivity(ZDR)ring and the correlation coefficient(CC)ring before the formation of mesocyclone can indicate the position of the updraft in the middle layer and the development of the vortex into the mesocyclone.When there is little difference in the strong reflectivity factor values,the larger the KDP,the heavier the precipitation.