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.

The daily rainfall data of 5 weather stations in east of Hexi corridor from 1971 to 2007 are used to analyze the temporal and spatial variation of precipitation events. The results show that there were three rainstorm events in east of Hexi corridor in recent 47 years, one occurred in the eastern mountain area of Hexi corridor and another two in the eastern plain areas in the 1980s and the 1990s. The total rainfall days, light rain, moderate rain and heavy rain days in the eastern plain areas of Hexi corridor presented decreasing trend, but in mountain areas they presented ascending trend. Total rainfall days decrease in plain areas was mostly due to the decreasing of light rain days there, while in mountain areas increase in total rainfall days was mostly due to the increasing of light rain events. The intensity of annual precipitation, light rain and heavy rain in the eastern plain and mountain areas of Hexi corridor presented significant increasing trend in recent 47 years, but moderate rain intensity decreased. The annual mean precipitation presented an increase trend in the eastern plain and mountain areas of Hexi corridor. The contribution of light rain and heavy rain to annual precipitation increased in plain areas, and the contribution of light rain and moderate rain to annual precipitation decreased slightly in mountain areas

Over the past 50 years, temperature in the Northwest China p resented a significant rising trend, while p recip itation change was different in different p lace. Warming and drying trend is evident in the whole Northwest China, but the local appearswarming and wetting phenomenon. With the global warming, glaciers retreat and snow line rises, permafrost melts, wetlands degradation, lakes shrink, river flows decrease, water resource becomes scarcer, and eco - environmental degradation. According to IPCC forecast results, the climate warming trend in this region in the future will be more p ronounced. The countermeasures to p rotect the ecological environment, imp rove the comp rehensive climate change monitoring system, launch specific research on the key regional climate changep rocesses, and other suggestionswere put forward.