A method is proposed for estimating monthly mean hourly direct, diffuse, an
d global solar radiation from annual stochastical models (correlation coeff
icients are higher than 0.99), using only actual and daily maximum solar el
evation and respective daily radiation as input data. The annual model (bas
ed on data collected on 45.8 degrees northern latitude) of monthly mean hou
rly global solar radiation relative to the monthly mean daily radiation is
found to be acceptable for latitudes between 40 and 50 degrees N, if compar
ed to other models. The same latitudinal validity is assumed for the annual
models of diffuse and direct solar radiation. Similar models for other lat
itudes could be derived if representative pyranometer data are available.