Diagnostic Analysis of Two Winter Snowstorm Events in Hunan Province
It is rare to have a snowstorm in Hunan Province.To improve the forecast accuracy rate of the intensity and area of snowstorm,this article diagnostically analyzes two snowstorm processes in Hunan during December 25-27,2021,and February 21-23,2022,by using conventional ground and upper-air data as well as the ERA-5 reanalysis data from European Centre for Medium-Range Weather Forecasts(ECMWF).The results show that both of the two snowstorm processes were featured with heavy intensity,extensive and overlapped impact area.However,obvious difference has been found in the two processes,that is,the accumulated snowfall in the December 2021 process was less than that in the February 2022 process,and the snow in the former process was mainly dry snow while that in the latter process was wet snow.The analysis of the difference causes suggests that:(1)The February 2022 process had stronger water vapor convergence,high extension height and thick thickness,and the dynamic condition was provided by the south branch trough and low vortex.In comparison,the moisture condition for the process in December 2021 was weaker,and the dynamic condition was provided by the forced lifting of the cold front.(2)The cold air of the December 2021 moved south from the lower layer,the specific cloud ice water content was large,and the temperature stratification was advantageous to the formation of dry snow.Then,during the February 2022 process,the air temperature dropped in the middle layer,the specific cloud ice water content was comparable to the specific cloud liquid water content in clouds,and the ground temperature was above O℃,so wet snow was dominant in this snowstorm event.
snowstormdiagnosis and comparative analysisdry snowwet snow
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