Comparison of measured and estimated monthly average daily global radiation in Shanghai, Nanjing and Hangzhou areas in East China

摘要

Several expressions have been used to estimate the monthly average daily global radiation on a horizontal surface from sunshine hours. These included original (linear) and modified (linear-logarithmic) Angstr?m-Black type regression functions, a quadratic function, a power relationship and one from a new Angstr?m-Black type logarithmic model. The models were compared on the basis of statistical error using the mean percentage error (MPE), root mean square error (RMSE) and the mean bias error (MBE). All the models performed well as estimators of the monthly average daily global radiation from sunshine hours but the non-linear models were better than the basic linear model. Overall, the quadratic model shows the best estimation of the monthly average daily global radiation on a horizontal surface. Based on the quadratic model, the measured and estimated monthly average daily global radiation for Shanghai, Nanjing and Hangzhou are compared. Just as the equations, the figures show good correlation between measured and estimated monthly average daily global radiation. The equations are listed as following: G/G0=0.15215+0.59138(S/S0)-0.07019(S/S0)2 (Shanghai) G/G0=0.13027+0.57425(S/S0)+0.00588(S/S0)2 (Nanjing) G/G0=0.11683+0.59479(S/S0)-0.03380(S/S0)2 (Hangzhou)