An observational and numerical study on the topography influence on the dust transportation

Through the observational statistic analysis and numerical simulation, a study on the influence of topography in eastern Asia on the dust transportation was conducted. The results showed that the high frequency dusty weather regions locate at the west of Inner Mongolia and southwestern Mongolia, especially at the hinterland of deserts, and also locate at the southern Xinjiang basin, especially at the south of it. The second high frequency dusty weather region is on the northeast of QinghaiTibet plateau. The dusty weather more frequently occurred at western Inner Mongolia and southwestern Mongolia is owing to some factors favorable for the dust storm formation besides plenty of dust particles can be provided there. Firstly, the canyon jet, which forms at south of AltaiSayan mountain, enhanced the surface wind speed and so in favor of the buildup of dust storm. Secondly, the southwardly downslope stream carrying a mass of dust particles from Sayan mountain was obstructed by the eastwardly canyon jet and so the dust particles concentrate there and dust storm boosts up. Thirdly, most mountains and hilly lands exist there, which produce the topographical wave and boost up the dust rising. The pattern that dust particles assemble in the atmosphere (form a severe dust storm) before they transport can be say a “dust relay station" forming there.The topography also affects the spreading of dust storm. The eastwardly canyon jet enhances the eastwardly transportation of dust particles from the “dust relay station". The downslope stream from the Sayan mountain and the topography forcing circumstream at the northeast of the Qinghai Tibet plateau enhances the southwardly transportation of dust partcles. Owing to the circum stream is so strong and the occurrence of cold front is so frequent, which transport the dust particles southwardly too, that the dust transportation in northern China is most