THE TRANSMITTANCE OF GLOBAL ULTRAVIOLET-RADIATION BY DIFFERENT CLOUDS TYPES

Basing on continuous ground ultraviolet (UV) measurements in Meteorological observatory of Moscow State University and results of model calculations the influence of different extended clouds forms upon UV radiation was analysed. With this purpose the transfer of global UV radiation C(Q) was used which is determined as a ratio of global UV radiation in the cloudy atmosphere to that under clear sky conditions. From model calculations C(Q) was shown to be determined mainly by the optical thickness of clouds. Simple analytic equations taking into account the 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) distributions were obtained for summer and winter periods.