Annual models of monthly mean hourly direct, diffuse, and global solar radiation at ground

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.