Abstract: Sandstorm is one of the main meteorological disasters in Inner Mongolia,China. In order to offer references for the prediction of sandstorm,by using sandstorm observational data of 116 weather stations in Inner Mongolia and the data of MICAPS during 2001-2015,this paper analyzed the atmospheric circulation in upper air and weather systems on the ground when there was sandstorms,and finally refined forecast indices of sandstorm for references. In detail,the analysis method is:refining the circulation background model of sandstorm based on the features of long wave at 500 hPa;refining the surface synoptic system of sandstorm by analyzing the features of the sea-level pressure field;refining the synoptic forecasting indices of sandstorm based on the position and intensity of the upper stream jet,cold core,frontal zone,and temperature advection,etc. of the upper level, and the pressure gradient,△P₃,△T₂₄ of the surface field;refining the sandstorm forecast target of physical factors based on the features of vorticity advection,vertical velocity,divergence of the upper level. The results show: sandstorm was the process of strong cold air outbreak southward,and had the characteristics of strong cold air,cold frontal zone and upper stream jet. Four styles of atmospheric circulations in upper air are responsible for the formation of sandstorm,including the style of moving high ridge,the style of sliding cold trough,the style of transverse trough and the style of rotating low vorticity. The strongly developed Mongolian cyclones and cold fronts were the major weather systems on the ground to result in sandstorm. Therefore,sandstorm forecast method should mainly focus on the locations of upper air jet axis,Ural high pressure ridge,upper frontal zone,Mongolian cyclones and cold front,centers of variable pressure on ground,overlapping areas of positive upper vortex advection and ground cyclones,and so on.

Key words: Inner Mongolia, sandstorm, weather system, forecast indices