Estimation of monthly mean hourly global radiation for latitudes in the 1°N–81°N range

Abstract

A way to estimate monthly mean hourly global radiation ( I ) from monthly mean daily global radiation ( H ) has been to use fits which give r = I H as a function of S 0 , the monthly mean daily maximum possible number of sunshine hours. In the present work it is shown that these plots are by no means of universal validity, but are clearly dependent on latitude for high latitudes. A new type of correlation is proposed, which gives r as a function of α , the solar elevation at mid-hour. The values of coefficients for the r versus α correlations are given for each month of the year, for the hours centered at 0.5 h, 1.5 h, 2.5 h, etc. from the true solar noon, and stations with latitudes in the 1°N–81°N range. The given coefficients are most likely valid for any latitude, north or south.