Abstract
The present study quantifies the relationship between ultraviolet-B (UVB) and broadband solar radiation (G) at Qena, Egypt. Data from 10-year hourly integrated totals for both UVB and G on a horizontal surface were used to determine the best fit between the two radiation types. On the basis of the correlation of determination (r(2)), a second-order polynomial was determined to provide the best fit. For the purpose of developing an empirical model to estimate UVB, all of the cases of UVB and G from a nine-year study from 2001 to 2009 were introduced. Monthly and seasonal empirical models, as well as a general expression, were established for UVB as a function of G. The values of r(2) ranged from 0.90 to 0.97. By using a new dataset of G, the estimated and the corresponding measured values of UVB were determined to be in good agreement whereby the values of r(2) between the two ranged from 0.91 to 0.98. In addition, the significance and performance of the regression forms were evaluated with the aid of several statistical analysis procedures. The values of the index of modeling (d) and coefficient of modeling efficiency (ME) were close to one. Moreover, the values of RMSE, mean bias error (MBE), and mean absolute error (MAE) were lower than the experimental errors. On the basis of this analysis, it has been determined that the suggested regression forms can be used to estimate UVB when it difficult to obtain measurements or when measurements are available only for limited periods at the studied region.