影响北京地区沙尘天气的源地和传输路径分析

利用1980—2005年的地面气象观测资料和沙尘天气过程的卫星遥感资料，逐次分析了影响北京地区沙尘天气过程的演变规律.借助地理信息系统，确定影响北京地区沙尘暴过程的源地和移动路径.结果表明:北京地区沙尘暴主要发生在春季和初夏， 4月最多；从历年统计资料看，北京地区沙尘次数总体呈逐渐减少趋势，但20世纪90年代后期，浮尘日数有所增加.根据沙尘源地的起沙情况，将沙尘源地划分为初始源地和加强源地.境外初始沙尘源地位于蒙古国中部和东南部地区，境内位于中国与蒙古国边界；境内加强源地位于我国内蒙古中西部的沙漠、戈壁和沙化草原地区，以及甘肃河西走廊和农牧交错带大面积的开垦地.影响北京地区沙尘天气的传输路径主要包括北路、西路和西北路，其中以西北路和偏北路为主. 

Analysis on Source Locations and Transportation Paths of Sand-Dusts Affecting Beijing

Based on the satellite RS data of sand-dust weather processes and themeteorological observational data from 1980 to 2005, the temporal variation of sand-dusts invading Beijing was analyzed. The source locations and transportationpaths of sand-dusts were determined in assistance with GIS. The results show that sand-dusts in Beijing occurred frequently in the spring and early summer, especially in April. Based on historic statistical data, the annual number of times of sand-dusts in Beijing is in the trend of decreasing in general, but it increased in late 1990s. According to their source locations, the sand-dusts are classified into two types, i.e. the initial-source and enhancive-source locations. The external initial-source locations are in the middle and southeast of Mongolia.The interna1 initial-source locations are in the area near the boundary betweenChina and Mongolia. The interna1 enhancive-source locations are in the desert,gobi and sandy grasslands of middle and west Inner Mongolia, and in the vast reclaimed lands of Hexi Corridor and agro-pastoral ectones of Gansu. There are three transportation paths: north paths, west paths and northwest paths. Most of theexternal source sand-dusts move along the north and northwest paths.