2021年冬季贵州东南部两次大范围暴雪天气过程对比分析

Comparative Analysis of Two Large-Scale Blizzard Weather Processes in Southeastern Guizhou in the Winter of 2021

摘要: 利用常规地面、高空和区域自动站观测资料、数值预报产品资料，对2021年12月25日夜间到26日白天和2022年2月21日夜间到22日白天先后发生在贵州东南部的两次大范围暴雪天气过程(以下简称“12.26”过程和“02.22”过程)的环流背景、影响系统、水汽条件、动力条件及温度条件等进行对比分析，探讨两次过程的异同点，并用EC细网格资料以及华南、华东、贵州WRF等中尺度模式降水产品对两次暴雪过程进行检验。得出：两次暴雪天气过程均是中高纬度地区两槽一脊形势下，东北到河套地区的低涡横槽东移转竖引导强冷空气南下与孟加拉湾东移的南支槽前强西南暖湿气流在贵州中东部地区强烈交汇与东移南压的低空切变线(低涡)共同造成；两次过程由于南支槽和西南低空急流强度不同，700 hPa影响系统不同以及水汽输送通道不同，因而造成过程降水相态、降温以及降雪强度和持续时间不同；“12.26”过程是在强冷空气西进过程中产生的，因而出现寒潮级别的剧烈降温，大气层结和天气现象有由雨转冻雨或雨夹雪到纯雪的转换过程，降雪时间持续12 h左右，影响时间相对较短，纯雪量相对小；而“02.22”过程发生前本地已在强冷空气控制下，大气层结为降雪层结结构，降雪持续时间长达24 h之久，造成累计降雪量大，积雪深度深，达到历史第二高值。EC数值预报对两次暴雪天气过程预报效果好，各家中尺度模式降水预报对强降雪过程预报提供了很好的参考依据。

Abstract: Using conventional ground, high-altitude, and regional automatic station observation data, as well as numerical prediction product data, a comparative analysis was conducted on the circulation background, impact system, water vapor conditions, dynamic conditions, and temperature condi-tions of the two large-scale snowstorm weather processes (hereinafter referred to as the “12.26” process and the “02.22” process) that occurred in southeastern Guizhou from night to day on De-cember 25, 2021 and from night to day on February 21, 2022. The similarities and differences of the two processes are discussed, and the EC fine grid data and precipitation products of mesoscale models such as South China, East China and Guizhou WRF are used to test the two snowstorms. The conclusion: the two snowstorm processes were both under the situation of two troughs and one ridge in the middle and high latitude area, jointly caused by the strong intersection of the strong cold air which was guided southward by the low vorticity with transversal trough from Northeast China to Hetao region shifting eastward and turning vertically and the strong southwest warm and humid air flow in front of the southern branch trough of the Bay of Bengal moving eastward in the central and eastern parts of Guizhou, and the low level shear line (low vortex) that moved eastward and pressed southward. The two processes have different precipitation phase states, cooling, and snowfall intensities and durations due to the different intensities of the south trough and the southwest low-level rapids, the different 700 hPa influence systems, and the different water vapor transport channels. The “12.26” process was produced in the process of the strong cold air moving westward, so there was a sharp cold wave level of cooling, the atmospheric stratification and weather phenomenon were transformed from rain to freezing rain or sleet to pure snow, the snow-fall lasted for about 12 h, the influence time was relatively short, and the pure snow was relatively small. However, before the “02.22” process occurred, the local area was already under the control of the strong cold air, the atmospheric stratification was snow stratification structure, the snowfall lasted for 24 h, causing a large accumulation of snow, deep snow depth, reaching the second highest value in history. The EC numerical forecast had good effect on the two snowstorm processes, and the mesoscale model precipitation forecast provided a good reference for the forecast of heavy snowfall process.