An Approach to Estimate Net Surface Shortwave Radiation on Clear-sky Days in Rugged Terrain Based on Remote Sensing Data

Remote sensing has become an important data source for estimating net surface shortwave radiation (NSSR) on glacier surface. However, for a small-scale mountain glacier, NSSR is influenced by not only the atmospheric environment and the sun-earth geometric system but also other surface features, such as terrain and the surface anisotropic reflectance characteristics. In this study, an integrated approach is proposed to obtain the spatial distribution of NSSR with the aid of a high-resolution digital elevation model (DEM), Landsat TM images, and MODIS (Moderate Resolution Imaging Spectrometer) atmospheric and BRDF (Bidirectional Reflectance Distribution Function) products. The estimation results of 18 typical observation periods closest to the corresponding MODIS overpass times show that NSSR exhibits very strong temporal and spatial heterogeneity in the Dayekou watershed of the Heihe River Basin, which is greatly affected by atmospheric and terrain environments. Verification results show that this algorithm performs well; the square of the correlation coefficient (R2) is 0.756, the mean bias error percentage (MBE%) are and the root-mean-square difference percentage (RMSD%) are -8.8% and 10.1%, respectively.