The typical black storms or sand-dust storms in the northwestern China are generated anddeveloped through an interaction between the specific large scale circulation pattern and mesosealesystems.The passing by/over a huge sand-abundant desert of a strong cold front with intensivefrontal zone at mid and lower levels is a necessary condition for the formation and development of ablack storm or a severe sand-dust storm.In order to investigate the mechanism of the sand-dustmobilization,transport and sedimentation during the black or sand-dust storms,a parameterizationscheme of sand-dust source-sink terms and an equation of transport for the sand-dust wereproposed and incorporated into the MM4 mesoscale model.The modified MM4 model was appliedto the“May 1993”black storm case and succeeded in reproducing the evolution of the weathersystems associated with the black-storm,the sand-dust concentration at surface layer and itsvertical distribution,and the sand-dust sedimentation and transport.Our results show that thenumerical simulating method by using a mesoscale model,with inclusion of an equation of thesand-dust transport and a parameterization scheme of the sand-dust source-sink terms,is apromising approach to study the mechanism for sand-dust mobilization,transport andsedimentation during a sand-dust storm event.
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