Long term measurements of the UV irradiance of inclined surfaces and visualization of UV exposure of the human body

Abstract

Intensities of UV radiation are usually measured at horizontal surfaces, as e.g. for the internationally standardized and used UV index (UVI). To specify the relevant UV exposure of the human body, or parts of its surface, the characterization of irradiances on inclined surfaces typical for the human body is needed. Therefore, an instrument was built to record, within two minutes, erythemally weighted irradiances in 27 directions and, simultaneously with a second radiometer, on the horizontal surface. By the end of this study more than 3000 measuring days at five different locations could be completed. The data provide a statistical base for the calculation of average UVI values on inclined surfaces at the five locations in Bavaria. The ratio of the irradiance on the inclined surfaces to the irradiance of the horizontal surface reaches its maximum of about 1.7 in winter on the mountain Zugspitze and 1.4 in Munich. The UVI values also were combined with a virtual surface model of the human body and by this UV exposure of the human body could be visualized.