Visualization of UV exposure of the human body based on data from a scanning UV-measuring system.

In general, measurements of UV radition are related to horizontal surfaces, as in the case of the internationally standardized and applied UV index, for example. In order to obtain more relevant information on UV exposure of humans the new measuring system ASCARATIS (Angle SCAnning RAdiometer for determination of erythemally weighted irradiance on TIlted Surfaces) was developed and built. Three systems of ASCARATIS have been in operation at different locations in Bavaria for 3 years, providing erythemally weighted UV irradiation data for 27 differently inclined surfaces every 2 min. On the basis of these data virtual three-dimensional models of the human body surface consisting of about 20,000 triangles could be created and each of these triangles coloured according to its UV irradiation. This allowed the UV exposure of the human body to be visualized for any kind of body posture and spatial orientation on the basis of real measuring data. The results of the UV measurements on inclined surfaces have shown that measuring UV radiation on horizontal surfaces, as done routinely worldwide, often underestimates the UV exposure of the human skin. Especially at times of the day or year with low solar elevations the UV exposure of parts of the human skin can be many times higher than that of the horizontal surface. Examples of three-dimensional modelling of the human UV irradiation are shown for different times of the day and year, altitudes above sea level, body postures and genders. In these examples the UV "hotspots" can be detected and, among other things, used to inform and educate the public about UV radiation.

Routine measurement of erythemally effective UV irradiance on inclined surfaces.

Measurements of erythemally weighted UV radiation are usually related to a horizontal surface. The radiation is weighted with the sensitivity of the human skin, but the surface of the human body has only few horizontal surfaces. Therefore the UV radiation on inclined surfaces has to be quantified to investigate UV effects on humans. To fulfill this task three fully automatic measuring systems were built to measure the erythemally weighted UV radiation in 27 directions within 2 min. This system measures routinely during the whole day and has now been in operation for nearly three years (in total 2000 measurement days) under any kind of meteorological conditions. The measurements provide the informations needed for further investigations concerning the UV effects on humans. The calibration of the erythemally weighting radiometers was performed in a way to provide reliable UV index measurements for all directions. The results of four exemplary measurement days in summer and winter for clear sky and overcast conditions are presented.

Simplified calibration for broadband solar ultraviolet radiation measurements.

Aspects of different calibration procedures for erythemally weighing broadband radiometers are presented in this study. These instruments are common in projects dealing with ultraviolet radiation effects on humans. Many erythemally weighing broadband radiometers are still operated using a single calibration factor (cf) that is provided with the instrument. The individual characteristics of every instrument are strongly dependent on the total ozone amount and the solar elevation. Therefore, a calibration procedure also has to take into account the ozone concentrations and the solar elevation to compensate for the effects of the individual characteristics and to provide comparable measurements. Given the variation of the ozone concentrations and the solar elevation, an individual cf has to be calculated for every measurement. Using a simplified version of the calibration procedure, which is presented in this study, can lessen this effort. Taking into account the relevant meteorological conditions for a measuring site, a single cf is calculated to compensate the individual characteristics of the instruments and therefore deliver comparable measurements with less effort.