Based on meteorological observation data, Doppler radar (CINRAD/CA) observation data, global topography data (1°×1°) and NCEP FNL 6-hour reanalysis data (1°×1°), the blizzard weather in spring in southeastern Inner Mongolia on 20 March 2019 was analyzed. The results show that the process was a typical backflow heavy snowstorm weather, the southwesterly warm and humid air at 700 hPa climbed along the low-level cold pad to produce frontogenesis, which was the main cause of this backflow blizzard. Obvious vertical wind shear and temperature differences generated because of the northeasterly jet at 925 hPa and southwesterly jet at 700 hPa, resulting in strong dynamic frontogenesis, and the dynamic frontogenesis mechanism played a significant role. The convergence of divergence at low-level was conducive to development of vertical upward movement. The southerly and easterly at 850 hPa transported water vapor to the southeast of Inner Mongolia. There was a strong inversion stratification between 850 hPa and 700 hPa, where the cold and warm air met violently. The north-south topography of the Greater Khingan Mountains had a blocking effect on the northeasterly ultra-low-level jet stream on the windward slope of the eastern foothills, which was conducive to accumulation of dry and cold air for a long time and increasing thickness of the cold pad in lower layer. Then the warm and humid air flow was forced to lift to higher layer, which was conducive to condensation of water vapor and increase of snowfall. At the strongest period of snowfall, there was a northerly in lower layer, and an obvious “S” shape in middle layer for warm advection on the radial velocity chart of radar. At the upper level, there was a southwesterly jet maintaining for a long time, and the shear lines of northwest-southwesterly wind and southwest-southeasterly wind maintained at the same time. There was a good correspondence between the strong snowfall and the warm and humid jet from southwest climbing on the cold pad on the radar radial velocity chart, which was instructive for short-term forecast and early warning.

Based on the conventional observation data in Hulunbuir of Inner Mongolia and reanalysis data from GDAS and NECP/NCAR, the characteristics of water vapor transport and budget during an extreme snowfall process in the northeast of Inner Mongolia in spring of 2016 were analyzed by using Euler method. Then, the water vapor sources, main water vapor transport channels and their contribution to water vapor transport of the heavy snowfall process were simulated by HYSPLIT model and clustered, and compared with the traditional results obtained by Euler method. The results are as follows: (1) Three water vapor streams from different sources met in northeastern part of Inner Mongolia, which had an important impact on the snowstorm process in Hulunbuir region. (2) Meridional and zonal transportation provided sufficient water vapor condition for the snowstorm process. The water vapor over snowstorm area mainly came from water vapor transport at the southern boundary in middle and upper levels and the western boundary with the westerly airflow. (3) The simulated results by HYSPLIT model showed that there were mainly three water vapor sources during the heavy snowfall process, they were the ocean surface west of the Xindi Island, the Japan Sea and the Balkhash Lake, respectively, and their contribution rates of water vapor over Hulunbuir area were roughly equivalent.