A deflation module for use in modeling long-range transport of yellow sandover 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 inform ation on emission intensity for use in modeling long-range transport of yel low sand over East Asia. In contrast to previous modules for Sahara and Aus tralian deserts, it includes three major predictors, the friction velocity, the surface humidity, and the dominant weather system. Comparison of the d eflation module results, using these three parameters together or separatel y, with observed data on dust deflation in April and July 1988, shows that the best estimate can be obtained by considering the three predictors toget her when we take the minimum of the total error ratio as the selection crit eria. It indicates that last two predictors provide a limitation for deflat ion and can decrease the number of false declarations from 23 to 7%, especi ally in the wet season. A regional long-range transport model for Kosa is i ntroduced, which considers various parameters such as particle size, transp ort, 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 partic les one peak appears close to the ground, while the other is in the middle troposphere.