A new method for estimating the regression coefficients in the formula relating solar radiation to sunshine

Abstract Following the manner of Prescott, most regression equations relating solar radiation to sunshine hours involve a factor a + bn/N, where a and b are constants dependent on the climate and the locality, and n/N represents the ratio of actual to potential duration of sunshine. Examination of the several published values of a and b shows that a is related linearly, and b is related hyperbolically, to the appropriate mean value of n/N. Use of these relationships to establish values of a and b results in a formula which provides more accurate estimates of radiation from sunshine data than by the extrapolated use of existing formulae.