A Synoptic model on East Asian Dust Emission And Transport

This study is concerned with the mechanism of dust storm development and the characteristics of the responsible synoptic systems. Two severe Asian dust storms occurred in spring 2002 are analyzed using synoptic and remote sensing data. The relations between the formation and movement of the dust storms and the evolution of the synoptic systems are examined. It is shown that a dust storm may develop when a synoptic system moves to the desert area of Northeast Asia with a surface wind speed exceeding 6 m s-1. Numerical simulations of the two dust storms are then carried out using a dust storm forecasting model which consists of three major components, including an atmospheric prediction model (together with a land surface model), a wind erosion scheme and a geographic information database. The performance of the model is verified with observations. It is found that the simulated dust plume travels farther than the real one if wet deposition is not considered in the model or if precipitation is incorrectly predicted. The simulated dust fluxes indicate that the dust source area is consistent with the desert region in Northeast Asia. However, the simulated dust source region is larger than the observed dust source region. This is probably due to the fact that the area with a wind velocity exceeding 6 ms-1 in the lowest model layer is over predicted. It is also shown that cold air flows in desert areas create favorable conditions for the development of dust storms. In the cold sector of the cyclone, the dust top is lower due to the descending air motion, while in the warm sector, the dust top is higher due to the ascending air motion. Finally, we present a conceptual model of dust storm generation and movement in East Asia on the basis of the above mentioned analysis.