一次中尺度对流风暴造成的内蒙古局地沙尘天气过程分析

利用气象信息综合分析处理系统（MICAPS）分析资料、NECP再分析资料、自动站观测资料、卫星红外云图、天气雷达资料等，对2018年初夏内蒙古锡林郭勒盟地区出现的一次典型局地沙尘天气过程进行了分析。结果表明：此次沙尘天气主要在高空冷涡环流背景下，由低层切变触发的强对流风暴造成，发生在强对流风暴的下沉气流中。沙尘发生时，地面气压从995.2 hPa跃升至1000.4 hPa，气温下降，风向从东北风（31°）突变为西北风（343°）。从天气形势看，在上冷下暖不稳定的大气层结状态下，对流云团发展旺盛，外流边界的强下沉气流促使地面形成大风，为此次短时沙尘天气提供了较好的动力条件。局地沙尘发生前，动力、热力条件有利于强对流天气的发生发展，高低层的辐散辐合、较强的上升运动及干燥的中层大气和下垫面，是局地沙尘天气产生的主要原因。

Local dust weather process caused by a mesoscale convective storm in Inner Mongolia Autonomous Region

In this paper, a typical local dust weather process in Xilingol League in the early summer of 2018 was analyzed using the analysis data from MICAPS (Meteorological Information Combine Analysis and Process System) and NCEP (National Centers for Environmental Prediction), data from the automatic weather stations, Satellite infrared cloud map, weather radar, etc.The dust weather is mainly caused by the strong convective storm triggered by the low-level shear under the background of the upper air cold vortex circulation and occurs in the downdraft of the strong convective storm.The observation data of the automatic weather stations in every five minutes interval show that when the dust occurs, the air pressure on the ground jumps from 995.2 hPa to 1000.4 hPa, the air temperature drops, the wind direction changes from the northeast (31°) to the northwest (343°), and the wind speed increases instantaneously.According to the weather situation, in the warm and unstable atmosphere, the convective cloud cluster is developing vigorously, and the strong downdraft at the outer boundary causes a strong wind near the ground, which provides a better dynamic condition for the short-term dust weather.Before the occurrence of local dust, the dynamic and thermal conditions are conducive to the occurrence and development of severe convective weather.The main causes of local dust weather are convergence at the lower level, divergence at a high level, strong upward motion, and dryness at the middle level and underlying surface.