Analysis of the dynamic causes of the extremely heavy snowfall in southern Xizang
Based on the MICAPS surface observation precipitation data of Xizang and the European Center for Me-dium-Range Weather Forecasts(ECMWF)ERA5 reanalysis data,the dynamic diagnostic method was used to analyze the extremely heavy snowfall in southern Xizang from January 16 to 18,2020.The results show that under the influ-ence of the trumpet topography in southern Xizang,the southerly and southwesterly warm and humid airflow climbs along the mountain slope,resulting in the formation of unstable atmospheric stratification between the low-level warm and humid updraft and the dry and cold air,which is conducive to the occurrence of blizzard weather.The strong convergence uplift at low altitude and the divergent suction at mid-high altitudes are the main dynamic mecha-nisms that cause heavey snowfall.The structure of vertical helicity"negative at bottom and positive on top"provides a useful indication for the prediction ofblizzard process,and strong snowfall will occur when the whole layer of helici-ty is a consistent positive value,and the intensity of blizzard increases with the rapid increase of the center value of the positive helicity in the lower layer,and the larger the center value,the stronger the intensity of snowfall.MPV1 is a vertical structure with"positive on top and negative at bottom",and when MPV2＜0,the absolute value of MPV1 and MPV2 increases rapidly,which is consistent with the increase in snowfall.
Extremely heavey snowfall on the plateauDynamic characteristicsVertical structureVertical helicityWet potential vortex
万方数据
维普
