THE TRANSMITTANCE OF GLOBAL ULTRAVIOLET-R ADIATION BY DIFFERENT CLOUDS TYPES

Basing on continuous ground ultraviolet (UV) measurements in Meteorolo gical observatory of Moscow State University and results of model calc ulations the influence of different extended clouds forms upon UV radi ation was analysed. With this purpose the transfer of global UV radiat ion C(Q) was used which is determined as a ratio of global UV radiatio n in the cloudy atmosphere to that under clear sky conditions. From mo del calculations C(Q) was shown to be determined mainly by the optical thickness of clouds. Simple analytic equations taking into account th e effects of surface albedo on global UV radiation and on C(Q) values were carried out. The attenuation of global UV radiation by different types of clouds was determined. Approximate formulae for the C(Q) dist ributions were obtained for summer and winter periods.