2021年温州地区首场降雪的双偏振雷达观测分析

Analysis of the First Snowfall in 2021 in Wenzhou with Dual Polarization Radar Data

基于常规观测资料、ECMWF再分析资料和双偏振雷达探测资料,对温州地区2021年首场降雪过程进行了分析,研究表明:(1) 此次降雪过程的环流形势表现为西高东低,引发降雪的主要天气系统是亚洲东岸大低涡及其向西伸出的横槽、700 hPa的西南风急流。(2) 在云底高度较高、云层厚度较浅薄的情况下,云顶温度较低、零度层高度较低、中层以下平均温度较低、无明显的中层暖层和中低层明显的逆温结构有利于降雪的形成。(3) 水平反射率因子较小,低于25 dBz,差分反射率因子较小,在1 dB以下,差分相移率较小,绝对值小于0.15 deg/km,这些双偏振雷达回波指标和HCL产品对温州地区的弱降雪判断有一定的参考价值。

Based on the conventional observation data, ECMWF reanalysis data and dual polarization radar data, the first snowfall process of 2021 in Wenzhou area is analyzed. The research shows that: (1) The circulation pattern of this snowfall process was shown as high in the West and low in the East, and the main synoptic systems caused the snowfall were the large vortex in the East coast of Asia, the horizontal through extended westward from the large vortex, and the 700 hPa southwest jet. (2) In the case of high cloud base height as well as shallow cloud thickness, the low cloud top temperature, the low zero-temperature height, the low mean temperature below the middle level, no obvi-ous warm layer in the middle level, but obvious inversion structure in the lower and middle troposphere were conducive to the formation of snowfall. (3) The dual polarization radar echo indexes such as the horizontal reflectivity factor smaller than 25 dBz, the differential reflectivity factor smaller than 1 dB, and the small differential phase shift rate when its absolute value less than 0.15 deg/km, and the HCL products can be certainly served as a reference for judging of weak snowfall in Wenzhou area.