DEPENDENCE ON CLOUDINESS AND SOLAR ALTITUDE OF GLOBAL SOLAR-RADIATIONRECEIVED AT 315 AND 545 NM ON HORIZONTAL SURFACES

The study of monthly mean half hourly values of global radiation recei ved at 315 (u.v.) and 545 nm (green) on a horizontal surface at Uccle (Belgium) in 1980 for clear (half hourly sunshine fraction sigma = 1) and overcast (sigma = 0) skies shows that for any solar altitude, glob al radiation received at 315 nm is less absorbed by clouds than radiat ion received at 545 nm. An explanation is given of the dependence on s olar altitude for clear skies of the ratio between monthly mean half h ourly values of global radiation received at both wavelengths, based o n considerations concerning the direct and diffuse components.