The erythemal dose rate (EDR) on the Earth's surface depends mainly on the solar zenith angle, column ozone, clouds, aerosols and surface albedo. Clouds are the main atmospheric agent in the modulation of EDR. Therefore, an investigation into the effect of clouds on the ultraviolet radiation (UVR) incidence is an important matter due to the effects of UVR on the biosphere. In this work, a case study is reported where EDR incidences are presented for an overcast-sky scenario of Altostratus (As) in Belo Horizonte (BH, 19.92ºS, 43.94ºO, 858 m, 331 km², Brazil). Although the attenuation yielded by the As layer, the incidence of UVR remained high setting in a threatening weather condition for people in outdoor activities.
solar ultraviolet radiation; clouds; cloud cover; UV-Index
