A deflation module for use in modeling long-range transport of yellow sand over East Asia

A deflation module of soil and sand dust loading, especially for Asian dust (called yellow sand or Kosa), has been designed to provide explicit information on emission intensity for use in modeling long-range transport of yellow sand over East Asia. In contrast to previous modules for Sahara and Australian deserts, it includes three major predictors, the friction velocity, the surface humidity, and the dominant weather system. Comparison of the deflation module results, using these three parameters together or separately, with observed data on dust deflation in April and July 1988, shows that the best estimate can be obtained by considering the three predictors together when we take the minimum of the total error ratio as the selection criteria. It indicates that last two predictors provide a limitation for deflation and can decrease the number of false declarations from 23 to 7%, especially in the wet season. A regional long-range transport model for Kosa is introduced, which considers various parameters such as particle size, transport, diffusion, and removal in detail. The model results show a reasonable agreement with the observations during Kosa episodes in April 1988. A size-resolved analysis explains the peculiar multi layered vertical distribution of dust at large distances from the source areas; that is, for fine particles one peak appears close to the ground, while the other is in the middle troposphere.