The Analysis And Research Of The Formation Mechanism That Sand-dust Storm At The North China

By using the PSU/NCAR MM5 model , we made a Numerical simulation aboutthe severe sand-dust storm that occured in the North China on 20March in 2002. We diagnosed and analysed the physical variation output field of the sand-dust storm, and we can get some concludes that how sand-dust storm occur and develop.The result shows that:the sand-dust storm occured in favorable climate background that is drought and rainless, the tilted trough and Mongolia cyclone are the important weather systems that caused the severe sand-dust storm, tilted trough and strong frontal zone caused the Mongolia cyclone developed and the clod front strengthened at surface, high jet and Ferrel circulation are the main reason that momentum spreaded downward from higher level and frontal zone strengthened on lower level. During the sand-dust storm, the high PV spreads evidently downward from the upper troposphere. The negative PV2 center on the level of 500hPa is corresponding with the center of severe sand-dust storm, and it is an important index for forecasting the sand-dust storm. Otherwise, the stratified atmosphere is stable when the severe sand-dust storm happened.The result of the terrain contrast test show:the Mongolia highland is of benefit to the development of cyclones of upper air and ground. The cyclone is stronger,the effect is evident. Therefore, the Mongolia highland is of benefit to the occurrence and development of the sand-dust storm at the North China.