内蒙古沙尘暴天气系统及预报指标探讨

根据21 世纪15 a 来出现在内蒙古的沙尘暴个例，归纳形成沙尘暴的高空环流背景和地面天气系统，提炼预报指标。结果显示：沙尘暴是强冷空气爆发南下的过程，具有冷空气强、锋区强、高空急流强的特征；造成内蒙古沙尘暴的高空环流背景可分为高脊移动型、冷槽下滑型、横槽型和低涡旋转型等四个类型；强烈发展的蒙古气旋和冷锋是造成沙尘暴的主要地面天气系统。沙尘暴预报应主要着眼于高空急流轴的位置、乌拉尔山高压脊、高空锋区、蒙古气旋及冷锋、地面变压中心、高空正涡度平流中心与地面气旋相叠置的区域等方面。

Weather system and forecast indices of sandstorm in Inner Mongolia

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.