The Instability Mechanism and Cause Analysis on the Precipitation Phase of a Blizzard in Spring
Based on conventional observation data,NCEP/NCAR 0.25°×0.25° reanalysis data and FY-2G TBB data,the formation mechanism of an extreme snowfall weather process in northeastern Inner Mongolia during April 19-21,2020 was analyzed.The results showed that:(1)The snowfall in this process was large and the precipitation phase was complicated.Several meteorological observing stations reported record-high precipitation in April.(2)The snowfall mainly caused by Cold vortex at 500 hPa and surface cyclone.(3)There was a northeast airflow between 850 hPa and ground that could be used as a cold cushion for the warm humid airflow at upper layer to climb along,leading to an elevated convection process in cold season.The tilted convection caused by conditional symmetric instability led to the extreme snowfall.(4)Tsurf ≤ 0 ℃,T925 ≤ 0 ℃,and T850 ≤-3 ℃ were three forecast index values of precipitation phase transformation.(5)The spatial boundary of precipitation phase was closely related to the location of the warm shear line at 700 hPa,and it moved with the shear line.(6)With the invasion of cold air from north,the descent of zero-temperature layer was one of the reasons for the change of precipitation phase.
Conditional symmetric instabilityElevated convectionDescending of 0 ℃ layer
万方数据
维普
