Empirical Estimation of Daytime Net Radiation from Shortwave Radiation and ancillary information

All-wave surface net radiation is greatly needed in various applications. Satellite data have been used to generate accurate shortwave radiation products, but limitations to practical applications arise due to interference from clouds. All-wave net radiation might be estimated empirically on the basis of shortwave radiation and other ancillary information. Several models have been previously reported, but estimated coefficients were determined from a limited number of ground observations and a comprehensive evaluation of these models using representative measurements from around the world is lacking. In this study, we compared seven commonly used empirical models using radiation measurements obtained from 326 sites around the world during 1991-2010. Meteorological data derived from re-analysis products and remotely sensed products during the same period were also used. The model evaluations were performed either in the global mode (all data used to fit the models) and adaptive mode (the data were divided into four subsets based on the surface albedo and vegetation index, and the models were fitted separately). Based on these extensive evaluations, we propose a new empirical approach that performs better than existing models.