Analysis of a typical heavy dust pollution weather in Semi-arid region- A Case Study in Eastern Qinghai

 Based on conventional meteorological observation data and particulate matter monitoring data, combined with traceability of pollution sources, the main causes of sand-dust heavy pollution and the characteristics of dust transmission in eastern Qinghai in May 2019 were analyzed by using the principles of meteorology and trajectory analysis.The results show as following：The heavy dusty weather is mainly affected by the development of the enhanced low-slot eastward of Lake Baikal. The low-slots carry strong cold air moving eastward ,leading to heavy pollution in the eastern part of Qinghai. During the dusty weather, the cold air from the Hexi Corridor was poured into the eastern part of Qinghai from the valley . The dust from Gansu Province entered and then transported from east to west to easdtern Qinghai,causing pollution. The presence of the inversion layer stabilizes the atmospheric stratification in the eastern boundary layer of Qinghai, which is not conducive to the outward spread of pollutants caused by surface turbulence activities. The long-term maintenance of dust that cannot be diffused in time is the main cause of heavy pollution. In the early stage of sand and dust weather, the humidity conditions in the eastern part of Qinghai gradually deteriorated. Before the sand-dust occurred, the sensible heat on the ground increased significantly. The water vapor in the atmosphere weakened, the air was dry, and the water vapor condition, which is an important condition for the formation of sand and dust,was poor. The dust storm transmission route affecting the eastern part of Qinghai is transmitted from southeast to northwest. The mixed layer height and static weather index of the EC numerical forecasts have a good predictive indication during the process. The results of the trajectory analysis also indicate that the dusty weather in the eastern part of Qinghai (Xining, Haidong, etc.) was caused by backward irrigation of sandfrom the Hexi Corridor, and affected Haidong and Xining areas under the influence of the terrain.