摘要
利用常规地面高空观测、中尺度自动气象站、双偏振雷达资料以及NCEP的1°×1°再分析资料,对2017年7月2—3日韶关市区引起内涝的一次大暴雨过程进行分析。结果表明:(1)高层强辐散、高空槽东移缓慢、低层切变线、低空急流以及有利的水汽条件,为该次暴雨的发生提供了有利的大尺度环流背景和天气系统配置。(2)低层强辐合触发了不稳定能量,而高层强辐散,为低层大气有抽气作用,加剧了气流的垂直上升运动,引起了短时强降水的发生。(3)双偏振雷达增加了3个基本量,对暴雨发生时间和位置的判断有了很大的提高:协相关系数CC的各层组合和剖面显示,0℃层高度下方均为0.99以上的单一相态降水,移入韶关的回波属于暖云降水;由差分反射率(Z_(dr))的分层显示看出,在1.5~3.0 km高度附近降水粒子大部分为0.8~1.5 dB,在小时降水达到大值时大部分处于1.0~2.0 dB,说明该次天气过程大多为中小降水粒子;差分相移率(K_(dp))是空中水含量的直接反映,通过K_(dp)与Z_(dr)相同仰角的显示分析,其大值区更应参考K_(dp)的表现,故分析应用时需综合判断。
Using conventional surface and upper-level observations,data from a mesoscale network of automatic weather stations and a dual-polarization radar as well as NCEP 1°×1°reanalysis,this work analyzes a flood-causing process of heavy rain that happened from July 2 to 3 in 2017.The result is shown as follows.(1)Favorable large-scale background circulation and allocated weather systems for the interested case included strong upper-level divergence,a slowly east-moving upper-level trough,a low-level shear,a low-level jet stream and sufficient amount of water vapor.(2)Strong low-level convergence triggered instability energy while strong upper-level divergence had a sucking effect on the lower atmosphere and increased vertically ascending motion of the air,resulting in the occurrence of short-term intense precipitation.(3)As three basic quantities were added to the dual-polarization radar,the timing and location of the heavy rain were able to be determined with great assurance.It is described below.As shown by both layered co-correlative coefficients(CC)and profiles,single-phase precipitation above 0.99 all appeared below the 0℃level.The echoes moving into the Shaoguan area are from warm-cloud precipitation.As shown in layered displays of difference reflectivity(Zdr),most of the precipitating particles are between 0.8 and 1.5 dB at the heights from 1.5 to 3.0 km and most of them are between 1.0 and 2.0 dB as the hourly precipitation is in the range of large values.It suggests that the heavy rain of interest is mostly made up of moderate and fine precipitating particles.Difference phase shift rate(Kdp)is the immediate response of airborne water content.As shown in the display of an elevation angle identical with both Kdp and Zdr,the performance of Kdp should be more taken into account when the large-value zone is examined,making a comprehensive approach necessary in both analysis and application.
作者
汪海恒
张曙
谢文杰
WANG Hai-heng;ZHANG Shu;XIE Wen-jie(Meteorological Bureau of Shaoguan,Shaoguan 512028)
出处
《广东气象》
2020年第6期30-34,共5页
Guangdong Meteorology
关键词
天气学
大暴雨
致涝
双偏振雷达
韶关地区
synoptics
unusually heavy rain
flood-causing
dual-polarization radar
Shaoguan area
