Estimation of the daily global solar irradiation at Corvallis, Oregon (U.S.A.) from the hours of bright sunshine, the daily temperature range and relative humidity

Simple empirical relationships based on the hours of bright sunshine, the daily temperature range and relative humidity have been developed to estimate the daily global solar irradiation at Corvallis, Oregon (U.S.A.). It is observed that the greater part of the variability in the daily solar radiation income at the surface is explained by changes in the available solar energy at the top of the atmosphere in the course of the year. The relationship based on the hours of bright sunshine yields estimates of the daily global solar irradiation which compare favorably with the measured values (coefficient of determination >0-90).