THE DIEECT SOLAR RADIATION AND THE ATMOSPHERIC TRANSPARENCY OVER HEXI REGION

Using the data of 3 years (1981-1983) of the two solar radiation stations in Minqin and Dunhuang of Hexi region, various kinds of attenuation of the direct solar radiation during the transmission process have been computed.There are three features in Hexi region, i.e.aridity.desert and narrow channel topograph.Their influence on the direct solar radiation appears as: in spring, the attenuation caused by the giant aerosol is almost equivalent to that caused by absorbing of the water vapour of the probable atmospheric precipitation of 0.5cm, the attenuant action of total aerosol is the most important among various factors; in summer, the aerosol and the cloud both are important attenuant factors; in winter.the action of the aerosol is more obvious than others.As for the annual attenuation of the direct solar radiation.the aerosol takes 35% (in which the giant aerosol takes 6%),the cloud takes a little less than 30%.the air molecule takes a little more than 20%, the water vapour takes a little less than 15%.