基于S波段双偏振雷达一次强雹暴过程观测分析

Observational Analysis of a Strong Hailstorm Based on S-Band Dual-polarization Radar

利用宁波S波段双偏振天气雷达资料、NCEP再分析资料、结合常规观测资料和实地冰雹调查资料,对2020年3月21日浙江省中北部一次强雹暴灾害过程(简称“03·21”过程)的天气背景和双偏振雷达回波演变特征进行分析。结果表明:(1)此次雹暴过程环流形势属于低层暖平流强迫类型,雹暴影响过程约4 h,雹暴A和B先以强的对流单体形态移动,在自西向东移动过程中分别加强为超级单体。(2)典型降雹时次具有明显的三体散射特征(TBSS),垂直剖面图上强回波(>50 dBz)伸展高度超过-20℃层,低层的弱回波,中高层悬垂回波明显。径向速度垂直剖面图上,雹暴低层辐合,其上叠加了辐散层,使得雹块得以继续形成和增长。(3)冰雹区出现了ZDR冰雹信号,对应的反射率因子(ZH)均大于65 dBz,差分反射率因子(ZDR)介于-2.0~0 dB,相关系数(CC)介于0.80~0.98;当结合ZH、ZDR、CC综合判断云中有冰雹粒子,CC<0.9时KDP的“空洞”区域也可作为判别大冰雹的依据之一。(4)HCL产品较好地反映了空中冰雹的分布和演变,根据低仰角的冰雹色标、同时结合零度层高度和雹云团下温度递减率值的大小,能更好地判断出冰雹发生的落区和尺寸。

Using Ningbo S-band dual-polarization radar data,NCEP reanalysis data,conventional observation data,and field hail survey data,the weather background and evolution characteristics of dualpolarization radar echo of a severe hailstorm disaster process in the central-northern of Zhejiang Province on 21 March 2020 is analyzed.The results show that:(1)The circulation situation of this hailstorm process which lasted about 4 hours,belonged to the type of low-level warm advection forcing.Hailstorms A and B first moved in the form of strong convective cells and strengthened into supercells,respectively,when moving from west to east.(2)At the typical hailing stages,there existed the obvious three-body scattering spike(TBSS).The extension height of the strong echo(>50 dBz)on the vertical profile exceeded-20 C,while the weak echo of the low layer and the hanging echo of the middle-high layer were obvious.On the vertical profile of radial velocity,the lower layer of the hailstorm converged,and the divergent layer was superimposed on it,which made the hailstorm blocks continue to form and grow.(3)The Zpr hail signal appeared in the hail area,and the corresponding Zh was greater than 65 dBz,Zpr was between-2.O and 0 dB,and Cc was between 0.80 and 0.98.When combined Zh,ZpR and CC to comprehensively judge that there were hail particles in the cloud,and C_(c)<0.9,the"hole"area of Kpp could also be used as one of the basis for judging heavy hails.(4)HCL products better reflected the distribution and evolution of hails in the air.According to the hail colour scale at low elevation,combined with the height of the zero-degree layer and the value of temperature decline rate under hail clouds,the falling area and size of a hail could be better judged.