苏南两次回流天气过程形势特征和降水相态分析  

Analysis of situation characteristics and precipitation types during two return-flow weather processes in southern Jiangsu Province

作　　者：王璐璐 钱俊龙 王丽芳 孙永 周彬 钱昊钟 WANG Lulu;QIAN Junlong;WANG Lifang;SUN Yong;ZHOU Bin;QIAN Haozhong(Wuxi Meteorological Bureau,Jiangsu Wuxi 214000,China;Jiading Meteorological Bureau of Shanghai,Shanghai 201800,China)

机构地区：[1]无锡市气象局,江苏无锡214000 [2]上海市嘉定区气象局,上海201800

出　　处：《气象科学》2023年第6期807-819,共13页Journal of the Meteorological Sciences

基　　金：江苏省预报员专项资助项目(JSYBY202012);上海市气象局“青年启航计划”。

摘　　要：利用常规观测资料、0.25°×0.25°FNL资料、微波辐射计资料和风廓线雷达资料,对发生在苏南的两次回流天气过程的环流特征、大气层结特征等进行分析。结果表明:高纬度地区500 hPa是两槽一脊的环流形势,近地面层持续受东北风影响,西南暖湿气流在底层冷垫上爬升,是回流降雪天气形势;从东北平原回流南下的冷空气湿度小,在降水中只起到了“冷垫”的作用。中低层西南暖湿气流差异导致两次降雪强度存在差异;近地面层的降温在雨和雪的区分判别上影响更大,统计2012—2022年初苏南地区8个降雪个例发现,苏南地区,满足T_(850)≤-4℃,T_(925)≤-3℃,T_(1000)≤1℃,T_(2 m)≤2℃这样的温度阈值条件时开始雨转降雪;当1515 gpm≤H_(700-850)≤1575 gpm,1289 gpm≤H_(850-1000)≤1317 gpm时,相态易由雨转雪。中低层西南气流、底层东北风的加强,2000 m左右高度风场的转变,短波槽(或切变线)触发了不稳定能量的释放,导致降雪发生;当中低层西南气流减弱转为西北气流后,大气水汽含量降低,降雪结束。Based on the conventional observation data,the 0.25°×0.25°FNL data,microwave radiometer data and the wind profile radar data,the circulation features,atmospheric junction characteristics in two return-flow weather processes that occurred in southern Jiangsu Province were analyzed.Results show that the synoptic situation of 500 hPa in the high latitude area is two troughs and one ridge,the near-surface layer is continuously affected by the northeast wind,the southwest warm and wet airflow climbs up along the bottom cold pad,which is a situation of return-flow snowfall weather.The cold air flowing southward from the northeast plain has little humidity and only plays the role of“cold cushion”in the precipitation.The differences of the southwest warm and wet airflow in the middle and low troposphere lead to different snowfall intensities of the two processes;the cooling near the surface layer has a greater impact on the discrimination between rain and snow,statistics of eight snowfall cases in southern Jiangsu Province from 2012 to early 2022 find that the possibility of snowfall should be considered in southern Jiangsu Province when meeting the temperature threshold conditions of T_(850)≤-4℃,T_(925)≤-3℃,T_(1000)≤1℃,T_(2 m)≤2℃;when 1515 gpm≤H_(700-850)≤1575 gpm,1289 gpm≤H_(850-1000)≤1317 gpm,the phase changes from rain to snow.The strengthening of the southwest airflow in the middle and low troposphere and the bottom northeast wind,the transformation of the wind field at the height of about 2000 m,the short-wave trough(or shear line)trigger the release of unstable energy,which leads to the occurrence of snow;when the southwest airflow weakens and turns to northwest airflow,water vapor content of the atmosphere decreases and the snowfall ends.

关 键 词：回流天气 西南急流 降水相态 温度层结 风廓线 

分 类 号：P458.121[天文地球—大气科学及气象学]