Validation of the Austrian forecast model for solar, biologically effective UV radiation UV index for Vienna

Since October 1995, a daily forecast of the UV index, as the irradiance of the biologically effective ultraviolet radiation, for the next day is publi shed for Austria, Europe, and world wide. The Austrian forecast model as we ll as the input parameters are described. By connecting the UV index with t he sensitivity of the photobiological skin types, a recommendation is given to select an appropriate sun protection factor of a sunscreen to avoid ove rexposure of the skin. The validation of the Austrian forecast model is don e by measurements of the biologically effective ultraviolet radiation colle cted between July 1996 and July 1998 at Vienna (48 degreesN, 16 degreesE), Austria. The forecast quality is evaluated by comparing the Austrian model with two statistical models used in Canada and the Netherlands. By using th e under-estimation of the UV index as criteria in the sense of radiation pr otection, the Austrian model shows a 12% underestimation over the whole yea r.