2021年11月7—9日辽宁省极端雨雪天气分析

Diagnostic analysis of the extreme rain-snow process in Liaoning province from November 7-9,2021

选用常规气象观测资料、人工加密观测资料和NCEP/NCAR格点资料,对2021年11月7—9日辽宁省极端雨雪天气进行诊断分析。结果表明:东北冷涡和地面气旋为此次极端雨雪天气的主要影响系统,对流层中低层辐合、高层辐散以及强的冷暖气流交汇,是产生极端雨雪天气的主要原因;高低空急流耦合和高空辐散抽吸作用,配合东北冷涡动力抬升作用,暖湿低空急流沿冷垫爬升,进一步加强了上升运动。暖湿急流为此次极端雨雪天气提供了充沛的水汽条件,暖湿急流的增强对应水汽辐合作用增强,配合低层冷垫和东北冷涡的动力抬升作用,对降雪有明显增幅作用;地面辐合线沿地形分布,触发了此次极端强降雪天气。地形阻挡导致地面冷空气堆积形成冷垫,是极端降雪天气发生的重要原因。温度层结差异是鞍山、岫岩雨雪相态差异的主要原因。具有冻结层特征的低层冷垫,为鞍山极端暴雪提供了有利的温度层结条件;融化层厚度和地面温度是岫岩出现冻雨的关键因素。

The conventional meteorological observation data,artificially enhanced observation data and NCEP/NCAR(the National Centers for Environmental Prediction and the National Center for Atmospheric Research)grid data were used to analyze the extreme rain and snow weather in Liaoning province from November 7-9,2021.The results show that the Northeast China Cold Vortex(NCCV)and the surface cyclone are the main influence systems of the extreme rain and snow weather.The convergence of the middle and lower troposphere,the divergence of the upper troposphere and the convergence of the strong cold and warm air flow are the main causes of the extreme rain and snow weather.The coupling of the high and low level jet and the high level divergence suction,together with the dynamic lifting effect of the NCCV,the warm and wet low level jet climb along the cold pad,which further strengthen the upward motion.The warm moist jet provides abundant water vapor conditions for the extreme rain and snow weather,and the strengthening of the warm moist jet corresponds to the strengthening of water vapor convergence,combined with the dynamic lifting effect of the low-level cold pad and the NCCV,and the ground convergence line distributes along the terrain,which triggers the extreme heavy snow weather.Terrain blocking leads to the accumulation of cold air on the ground to form cold air cushion,which is an important reason for extreme snowfall.The difference of temperature stratification is the main reason for the difference of rain and snow phase between Anshan and Xiuyan.The low layer cold air cushion with the characteristics of freezing layer provides favorable temperature stratification conditions for the extreme snowstorm in Anshan.The melting layer thickness and ground temperature are the key factors for the occurrence of freezing rain in Xiuyan.