Evaluation of three models for calculating daily global solar radiation at Yushu, Tibet

This study presents an analysis of the relationship between global solar radiation and the sunshine duration at Yushu using linear regression methods (Linear model, Quadratic model and Cubic model), which were previously used by researchers commonly. The global solar radiations estimated from the three models were compared with the measured values. Performance of the three models is evaluated by the following statistical error tests: the mean percentage error (MPE), mean bias error (MBE) and root mean square error (RMSE). Correlation coefficient R is also used to evaluate the accuracy of the models. Comparisons show that all the three models used in the present paper give very good results, and that the Quadratic method presents comparatively more accurate results than other models.