Spatial and Temporal Change Characteristics and Circulation Background of Sandstorm in Gansu Corridor

Based on the observation data from weather station during the past 50 years and the NCEP/NCAR reanalysis climate data, the spatial distribution characteristics and temporal variation laws of the sandstorm in Gansu Corridorare analyzed, also and the circulation background that isfavourable for the occurring of the sandstorms in North China are analyzed. The results show that the spatial distribution of the sandstorms in Gansu Corridoris product of arid and unstable underlying surface transition zone. It mean that, in the same atmospheric conditions, the ground surface status determine mainly the spatial distribution of sandstorm. The temporal variation laws of the sandstorm in Gansu Corridorare related to strong wind, and the same things are true for their daily, annual, interannual and interdecadeal variations. That is, on a certainly ground surface, the atmospheric status determinate the temporal variation of sandstorm. The EOF analyese for sandstorm show that the sandstorm day numbers have a clearly rise trend from the end of last century to the beginning of this century and the rising value is about the third to quarter of total falling one.