A Study on Parameterization of Surface Albedo over Grassland Surface in the Northern Tibetan Plateau

The relationship of surface albedo with the solar altitude angle and soil moisture isanalyzed based on two-year (January 2002 to December 2003) observational data from the AWS(Automatic Weather Station) at MS3478 in the northern Tibetan Plateau during the experimentalperiod of CEOP/CAMP-Tibet (Coordinated Enhanced Observing Period Asia-Australia Monsoon Projecton the Tibetan Plateau). As a double-variable (solar altitude angle and soil moisture) function,surface albedo varies inconspicuously with any single factor. By using the method of approximatelyseparating the double-variable function into two, one-factor functions (product and addition),the relationship of albedo with these two factors presents much better. The product and additionalempirical formulae of albedo are then preliminarily fitted based on long-term experimental data.By comparison with observed values, it is found that the parameterization formulae fitted by usingobservational data are mostly reliable and their correlation coefficients are both over 0.6. Theempirical formulae of albedo though, for the northern Tibetan Plateau, need to be tested by muchmore representative observational data with the help of numerical models and the retrieval ofremote sensing data. It is practical until it is changed into effective parameterization formulaerepresenting a grid scale in models.