Global solar radiation estimation from relative sunshine hours in Yemen

The existing measurements of global solar radiation and sunshine duration for Yemen are examined. The errors of estimating solar radiation from sunshine hour measurements using Angstrom's relation are evaluated. As a simple predictor for global radiation, an average Ansgtrom relations in the form H/H0 = 0.315 + 0.3612 n/N for all stations is evaluated. Other Angstrom correlation relations are also proposed by classifying the stations under into four groups. The estimated results are compared and seem to be satisfactory in the latter case.