Regional Division of Sand-Dust Events in East Asia from the Standpoint of Synoptic Climatology

摘要

This study attempted to categorize the regions in East Asia by frequency of occurrence of sand-dust storms, recent trends in such occurrences, routes of cold air invasion causing sand-dust storms and synoptic climatological situations. By referring to the results of previous studies, there were found to be five regions, A to E, from northwestern China to Japan, in which clearly different characteristics and synoptic climatological conditions occurred. A table is given as a summary, describing the regions briefly. In Regions A and B, sand-dust storm frequencies are decreasing because of weak cold air invasion from the anticyclone over Siberia under the influence of global warming during recent years. In Region C, two zones (routes) with lower temperatures run from NE to SW in eastern Mongolia and its adjacent regions. These zones (routes) are related to active cyclogenesis in the area of 45-50° N, 115-120° E in spring during the past few decades. The developed cyclones induce an influx of lower temperature air from the higher latitudes behind the cold front extending southwestwards from the center and this inflow causes heavy sand-dust storm occurrence in eastern Mongolia, eastern Inner Mongolia, the Beijing region and their surrounding areas. This cyclogenesis is occurring more frequently earlier in spring under the influence of global warming. In Regions D and E the transport and spread of sand-dust particles predominates.