一次冻雨天气的云雷达回波特征分析

Characteristics of Cloud Radar Echoes duuring a Freezing Rain

利用2014年12月10—12日的地面和探空资料、ECWMF再分析资料、Ka波段毫米波云雷达资料,采用特征分析、物理诊断量方法及回波特征分析方法,得到了较天气雷达更精细的垂直微观特征,对贵州冻雨的形成和演变提供了新的观测事实。结果表明:(1)此次冻雨过程地面温度在0℃附近,且云系形成后的温度随高度下降始终维持在-10～0℃之间,为过冷暖雨过程。(2)冻雨在初生、成熟及消亡阶段的回波强度随高度下降逐渐增大,强度值为-30～12dBz。空气垂直速度集中在-0.4～1.6m/s之间,粒子下落速度集中在2.4m/s以内。(3)冻雨初生及消亡阶段上升运动弱,粒子尺寸小。成熟期间,上升气流加强,小粒子所占比例减小,大粒子增多。云体中下部谱宽大值区和强反射率因子对应,反映了液态过冷水下落过程中的碰并增长结果。

Based on the normal observation data from 10 to 12 December 2014,ECWMF reanalysis data and Ka-band millimeter-wave cloud radar data,using the methods of physical diagnosis and echo characteristics analysis,the more refined vertical micro features,compared with weather radar,are obtained.The new formation and evolution observations of freezing rains in Guizhou are provided.The result shows:(1)The ground temperature in the freezing rain process was near 0 ℃.After clouds had formed,its temperature decreased with height and always maintained between-10 and 0 ℃.It is a supercooled warm rain process.(2)The echo intensity of the freezing rain increased gradually with decreasing height in the primary,maturation and extinction stages,ranging from-30 to 12 dBz.The vertical velocity of the air is concentrated in the range of-0.4 to 1.6 m/s,and the velocity of the particles falls within 2.4 m/s.(3)The ascending motion was weak and the particle size was small in the primary and extinction stages of the freezing rain.In the mature stage,the updraft increased,then the proportion of small particles decreased,and the number of large particles increased.In the middle and lower parts of the cloud,the large value region of the spectrum corresponded to the strong reflectivity factor,which reflects the collision growth in the falling process of supercooled liquid water.