Validation of five global radiation models with measured daily data in China

Two sunshine based and three air temperature based global radiation models are calibrated using daily data in Jan. 1 1994-Dec. 31 1998 at 48 stations all over China. The Nash-Sutcliffe equation (NSE) is used as the model evaluation criterion. The sunshine based models are suitable for daily global radiation estimation. The averaged NSE value of the Angstrom model is 0.83, and the maximum value is 0.91. The maximum NSE value of the Bahel model is 0.92 with an averaged value of 0.84. The models that use air temperature as the input variable are not suitable for daily global radiation estimation in China. The averaged NSE values of the three air temperature based models (Bristow-Campbell model, Allen model and Hargreaves model) are not larger than 0.47. A logarithmic relationship between the daily global radiation/ daily extra-terrestrial solar radiation (RGIRA) and the temperature difference between the maximum and minimum daily air temperature (T-M - T-m) is found in the present study. A new daily global radiation model that is a function of RA, sunshine hours and T-M - T-m is designed, which gives an averaged NSE value of 0.85 and a maximum value of 0.92. (C) 2003 Elsevier Ltd. All rights reserved.