In a recent study, melanoma incidence rates for Austrian inhabitants living at higher altitudes were found to increase by as much as 30% per 100 m altitude. This strong increase cannot simply be explained by the known increase of erythemally-weighted irradiance with altitude, which ranges between 0.5% and 4% per 100 m. We assume that the discrepancy is partially explainable by upwelling UV radiation; e.g., reflected by snow-covered surfaces. Therefore, we present an approach where the human UV exposure is derived by integrating incident radiation over the 3D geometry of a human body, which enables us to take upwelling radiation into account. Calculating upwelling and downwelling radiance with a radiative transfer model for a snow-free valley and for snow-covered mountain terrain (with albedo of 0.6) yields an increase in UV exposure by 10% per 100 m altitude. The results imply that upwelling radiation plays a significant role in the increase of melanoma incidence with altitude.

The vitamin D₃-weighted UV exposure of a human with vertical posture was calculated for urban locations to investigate the impact of orientation and obstructions on the exposure. Human exposure was calculated by using the 3D geometry of a human and integrating the radiance, i.e., the radiant energy from the direct solar beam and the diffuse sky radiation from different incident and azimuth angles. Obstructions of the sky are derived from hemispherical images, which are recorded by a digital camera with a fisheye lens. Due to the low reflectivity of most surfaces in the UV range, the radiance from obstructed sky regions was neglected. For spring equinox (21 March), the exposure of a human model with winter clothing in an environment where obstructions cover 40% of the sky varies by up to 25%, depending on the orientation of the human model to the sun. The calculation of the accumulated vitamin D₃-weighted exposure of a human with winter clothing walking during lunch break shows that human exposure is reduced by the obstruction of buildings and vegetation by 40%.

Die Vitamin-D₃-gewichtete UV-Exposition eines aufrecht stehenden Menschen wurde für ausgewählte urbane Umgebungen bestimmt, um den Einfluss der Verschattung durch Gebäude oder Bewuchs auf die Exposition zu untersuchen. Die Exposition wird berechnet unter Berücksichtigung der Strahldichte, also der Strahlungsenergie von direkter Sonnenstrahlung und diffuser Himmelsstrahlung aus verschiedenen Einfalls- und Azimutwinkeln und der 3 D-Geometrie eines Modellmenschen. Die Verschattung wird durch Hemisphären-Bilder bestimmt, die mithilfe einer Fotokamera mit Fischaugenobjektiv aufgenommen wurden, wobei angenommen wird, dass die Strahlung verschatteter Himmelssegmente vernachlässigbar klein ist. Dadurch werden den Himmel verdeckende Hindernisse räumlich hochaufgelöst erfasst und als Input in das Expositionsmodell eingegeben. Die Vitamin-D₃-gewichtete Exposition betrug an einer bebauten Straße am 21. Dezember zu Sonnenhöchststand ungefähr 50 % und am 21. März 70 % von der Exposition einer hindernisfreien Umgebung. The vitamin D₃ weighted UV exposure of a human with vertical posture was calculated for specific urban locations to investigate the impact of shadowing by buildings or vegetation on the exposure. The exposure is calculated by taking into account the radiance, i. e. the radiant energy from direct solar radiation and diffuse sky radiation from different incident and azimuth angles and the 3 D geometry of a human model. Obstructions shading the sky radiance are derived in high spatial resolution from hemispherical images, taken by a digital camera with a fisheye lens. The radiance from shaded sky regions is neglected in the UV. The derived shadowing information is used as input in the exposure model. The vitamin D₃ weighted UV exposure on a street within a city on December 21 at noon is approximately 50 % and on March 21 at noon 70 % of the exposure compared to an unobstructed location.