1.Introduction Commonly in late winter and spring, as cold and dry continental polar air mass from northern latitudes moves southward or south-southeastward to exchange heat and moisture with warm and moist air mass at lower latitudes, the two different air masses meet in Mongolia or Inner-Mongolia of China to form the cold front or cold air outbreak (Wang,et al.,2008,Sun et al,2001).Given suitable atmospheric conditions, the strong surface winds associated with the baroclinic system of cold front lift dust from the dry sandy surface of the deserts in western China produce so-called Asian Dust Storms (ADS).