2018年1月杭州市连续雨雪过程中雨雪转换气象条件分析  

Analysis on Meteorological Conditions of Rain-snow Transformation in the Hangzhou Continuous Rain-Snow Process in January 2018

作　　者：陈光宇[1] 陈勇明[1] 沈杭锋[1] 廖振杨 勾亚彬[1] 朱泽华 Chen Guangyu;Chen Yongming;Shen Hangfeng;Liao Zhenyang;Gou Yabin;Zhu Zehua(Hangzhou Meteorological Office,Hangzhou 310051,China;Hangzhou Xiaoshan Meteorological Office,Hangzhou 311201,China)

机构地区：[1]杭州市气象局,杭州310051 [2]杭州市萧山区气象局,杭州311201

出　　处：《气象与环境科学》2023年第2期67-75,共9页Meteorological and Environmental Sciences

基　　金：杭州市气象局科技计划项目(QX201912)。

摘　　要：利用2018年1月下旬杭州及周边地区各气象观测站的逐小时地面气象要素观测资料、ERA-Interim逐6 h再分析资料,以及同时期微波辐射计、风廓线雷达和双偏振雷达资料,采用等熵位涡分析、物理量诊断等方法,分析了杭州市一次长时间连续雨雪过程的天气成因,并讨论了雨雪转换前后的气象要素特征。天气背景分析表明,200 hPa脊后辐散区和强西风急流提供了强上升运动,500 hPa倒“Ω”阻塞形势和以295 K等熵面高位涡值代表的低层冷空气提供了持续冷源。分析雨雪转换前后的气象要素发现,当700 hPa温度在-1℃以下,850—925 hPa为东北风,冷层温度低于-4℃时,杭州以降雪为主,反之将出现雨雪转换。不同的暖层和冷层厚度是造成27日降水相态不同的原因。温度高于-1℃暖层和温度低于-3.5℃冷层的厚度,可作为雨雪相态的判断指标。微波辐射计和风廓线雷达探测资料分析结果表明,雪转雨时,温度的变化开始于700 hPa高度,并逐渐向下传导,700 hPa温度的变化时间较850—925 hPa的提前约4~6 h,待低层冷层强度明显减弱后由降雪转为降雨。双偏振雷达差分反射率(Z_(DR))、零阶滞后相关系数(CC)和相态识别产品(HCL)分析结果表明,25日、27日两次雪转雨过程中25日层结温度较27日的低,冷层强度也较27日的强,是25日未出现纯雨的原因。通过分析雷达产品可大致分辨层结气温分布特征,并判断降水相态。Based on the hourly meteorological observation data of Hangzhou and nearby cities,ERA-Interim 6 h reanalysis data,microwave radiometer data,wind profiler data and dual polarization weather radar data in late January 2018 as well as the isentropic potential vorticity method and diagnostic analysis,the causes for a long-time continuous rain and snow process and the meteorological element characteristics before and after the conversion of rain and snow in Hangzhou are analyzed.The analysis of synoptic background indicates that strong updraft flows are related to divergence zone and strong westerly jet at 200 hPa.The 500 hPa inverted“Ω”blocking situation and the low-level cold air represented by high potential vorticity(PV)at 295 K isentropic surface provide a continuous cold source.The analysis of the meteorological elements before and after the rain-snow conversion suggests that when the 700 hPa temperature is below-1℃,there is northeasterly wind in 850925 hPa,and when the cold-layer temperature is lower than-4℃,snow falls in Hangzhou.Otherwise,the conversion between rain and snow will occur.Different thicknesses of melting layer and cold layer led to different precipitation phases on the 27th.The thicknesses of warm layer with temperature above-1℃and cold layer with temperature below-3.5℃can be taken as a criterion for the phase state of rain and snow.Microwave radiometer and wind profiler data shows that when snow turns to rain,temperature change starts from the 700 hPa height,and gradually develops downward.The occurrence time of temperature change at 700 hPa is about 46 hours earlier than that in 850925 hPa.After the intensity of the cold layer in the lower layer weakens significantly,snow turns into rain.The differential reflectivity(Z DR),zero-order lag correlation coefficient(CC)and phase recognition products(HCL)of dual polarization weather radar show that the reason why there was no pure rain on the 25th was that the stratification temperature on the 25th was lower than that on the 27th and th

关 键 词：雨雪转换 环流形势 等熵位涡 暖层 冷层 

分 类 号：P458.3[天文地球—大气科学及气象学]