湖南冬季两次暴雪过程的对比诊断分析

利用常规地面和高空观测资料及欧洲中心ERA-5再分析数据，对2021年12月25—27日（21·12）、2022年2月21—23日（22·02）发生在湖南的两次暴雪过程进行诊断分析。两次暴雪过程有强度大、影响范围广，暴雪落区较为重合的特点。两次暴雪过程也表现出明显差异，21·12过程的累计降雪量小于22·02过程，但21·12以干雪为主，22·02以湿雪为主。分析差异的成因发现：（1）22·02过程水汽辐合强度强、延伸高度高、厚度厚，动力条件由南支槽和低涡提供；21·12过程水汽条件相对弱，动力条件由冷锋强迫抬升提供。（2）21·12过程冷空气从低层南下，云中冰相粒子比例大，温度层结满足干雪条件；22·02过程中层气温下降，云中冰相粒子与水相粒子共存，地面气温在0℃以上，故以湿雪为主。

Diagnostic Analysis of two Snowstorm Event during Winter in Hunan Province, China

This paper based on conventional sounding data, surface observation data, ECMWF 0.25°×0.25° reanalysis data to diagnose two snowstorm processes occurred in Hunan on December 25-27(th), 2021 (21.12) and February 21-23rd, 2022 (22.02) . The intensity of the two snowstorm processes was heavy, the impact area was wide and overlapping. The results show that:The two snowstorms showed obvious differences,the accumulated snowfall in the process of 21.12 is less than that in the process of 22.02, but 21.12 shown as wet snow, 22.02 shown as dry snow. It is found that: (1)The process of 22.02 has stronger water vapor convergence , and the dynamic conditions are provided by the south branch trough and low vortex; The process of 21.12 process has weaker water vapor convergence, and the dynamic condition is provided by the forced lifting of the cold front. (2) The cold air of 21.12 flows by the lower layer, the specific cloud ice water content is large, and the temperature stratification is advantageous to dry snow; The cold air of 22.02 flows by the middle layer, the specific cloud ice water content is comparable to the specific cloud liquid water content, and the temperature stratification is advantageous to wet snow.