2024年2月初湖北极端冰冻过程的观测和成因分析  

Observational and causal analysis of the extreme freezing in Hubei Province in early February 2024

作　　者：陈璇[1] 钟敏[1] 陈赛男[1] 罗昱 熊思章 鲁易 刘瑞雪 CHEN Xuan;ZHONG Min;CHEN Sainan;LUO Yu;XIONG Sizhang;LU Yi;LIU Ruixue(Wuhan Central meteorological Observatory,Wuhan 430074)

机构地区：[1]武汉中心气象台,武汉430074

出　　处：《暴雨灾害》2024年第6期668-679,共12页Torrential Rain and Disasters

基　　金：湖北省自然科学基金项目(2023AFD096)。

摘　　要：2024年2月初湖北省遭受了一次极端冰冻天气过程,期间经历了冻雨、冰粒和雪等多种降水相态变化,其中冻雨强度为当地1981年以来最强。为给复杂冰冻天气过程的准确预报及精细化预警服务提供参考依据,利用常规气象观测、双偏振雷达和再分析资料,对湖北此次极端冰冻过程的基本观测特征及成因进行分析。结果表明:(1)此次过程的环流形势表现为,南支槽和副热带高压共同影响,西南气流与偏东路冷空气长时间交汇,西南暖湿气流叠置在低层冷空气之上,垂直方向上存在有利于冻雨发生的“冷-暖-冷”温度夹心层结。700 hPa水汽通量异常偏强、700—800 hPa温度异常偏高和925 hPa温度异常偏低是此次冻雨强度具有极端性的主要原因。(2)降水相态与垂直温湿层结的关系分析表明,云顶伸展高度、融化层和低层冷垫的厚度及强度是决定降水相态的关键因子,湖北省此次过程冻雨和冰粒均为融化机制降水,冰粒比冻雨云顶高度更高、融化层厚度和强度更弱、低层冷垫厚度和强度更强。(3)此次极端冻雨的双偏振雷达特征表现为强回波主要集中在融化层2~3 km高度附近,有明显的0℃层亮带特征,回波强度为30~45 dBz,最强可达50 dBz;在融化层及以下,相关系数维持在0.7~0.95,存在明显的梯度大值区;差分反射率为正值,强度在1~3 dB,最大达4 dB,与降雨没有明显差异,但与纯雪为负值差异较大。An extreme freezing weather occurred in Hubei during the early of February in 2024,which accompanying freezing rain,ice pellets,and snow occurred and the intensity of freezing rain ranks first since 1981.Based on conventional meteorological observations,dual-polarization radar,and reanalysis data,the characteristics of observation and the cause of extreme freezing rain process are analyzed to provide reference for accurate forecasting and refined warning services of complex freezing weather processes.The results are as follow.(1)This process occurred under the combined influence of the subtropical trough and the subtropical high,with the long-term convergence of the cold air from the east route,forming a typical circulation pattern where the southwest warm and moist air flows are superimposed on the low-level cold air,and a"cold-warm-cold"temperature sandwich structure conducive to the occurrence of freezing rain is formed in the vertical direction.The abnormally strong water vapor flux at 700 hPa,the abnormally high temperature at 700-800 hPa,and the abnormally low temperature at 925 hPa are the main reasons for the extreme intensity of the freezing rain.(2)The analysis of the relationship between precipitation phase and vertical temperature and humidity layer structure indicates that the cloud top height,the melting layer,and the thickness and strength of the low-level cold pad are the key factors determining the precipitation phase.In this process in Hubei Province,both freezing rain and ice pellets are melting mechanism precipitation,with ice pellets having a higher cloud top height,weaker melting layer thickness and strength,and stronger low-level cold pad thickness and strength than freezing rain.(3)The dual-polarization radar characteristics of this extreme freezing rain are manifested as strong echoes mainly concentrated near the 2~3 km height of the melting layer,with a clear 0℃ layer bright band feature,and echo intensity of 30~45 dBZ,the strongest reaching 50 dBZ,in and below the melting layer,the co

关 键 词：极端冻雨 冰粒 温湿层结 双偏振雷达特征 

分 类 号：P458[天文地球—大气科学及气象学]