清远一次超级单体降雹的双偏振雷达特征分析

Analysis of the Characteristics of Polarimetric Weather Radar for a Super-cell Hail in Qingyuan

利用双偏振天气雷达对2016年4月26日清远地区一次超级单体降雹进行分析,得出降雹单体具有BWER、三体散射特征。超级单体强回波中心深厚且回波顶高,速度图上低层深厚持久的中气旋和高层强烈辐散是此次过程主要特征。单体降雹前低层ZDR值在3 d B以上,降雹时ZDR值趋近于0并且0值区范围扩大;差分相移率KDP和相关系数CC特征表明同一层面上单体存在着雹水共存、干冰雹粒子、大冰雹三种状态,冰雹下落过程中表面层融化形成水膜使差分相移率值增大。HCL特征显示HA区与指状回波对应,对流云前端有BD区。降雹单体内雹区深厚,4 km以下雹区周边以过冷却水滴为主,4 km以上为冰粒。超级单体的VIL值有2次明显的跃增过程,第1个跃增过程对应单体开始降雹,第2次过程对应大范围降雹。

Using the data of a polarimetric weather radar, a super-cell hail on April 26, 2016 is studied for the region of Qingyuan. It was determined that the hailing cell was characterized by BWER and three- body scattering. Its center of intense echo was deep and the echo top was high, with deep and long-lasting mesocyclone and intense upper-level divergence, the main characteristics of this hail process, as shown in the velocity chart. Prior to the hail, low-level ZDR was more than 3 dB, but during the hail it came close to zero and the zero zone was increasing. The differential phase-shift rate KDP and correlation coefficient CC showed that three states of hail water, dry ice and hail droplets and giant hails coexisted in the cell at the same level and during the fall of hail, the surface layer melted to form a film of water so as to increase the differential phase-shift rate. As shown in the HCL characteristics, the HA zone was corresponding to the finger-shaped echo and the BD zone was in the front part of the convective cloud. Within the hail cell, the hail zone was deep. Supercooled water droplets were mainly in the layer below 4kin while ice droplets were mainly above it. The VIL of the super-cell had two obvious processes of abrupt increases, with the first one corre- sponding to the beginning of hailing from the cell and the second one to large-scale hailing.