Modelling UV irradiances on arbitrarily oriented surfaces: effects of sky obstructions M. Hess and P. Koepke Meteorological Institute of the L.-M. University, Munich, Germany
Abstract. A method is presented to calculate UV irradiances on inclined surfaces that
additionally takes into account the influence of sky obstructions caused by
obstacles such as mountains, houses, trees, or umbrellas. With this method
it is thus possible to calculate the impact of UV radiation on biological
systems, such as, for instance, the human skin or eye, in any natural or
artificial environment. The method, which consists of a combination of
radiation models, is explained here and the accuracy of its results is
demonstrated. The effect of a natural skyline is shown for an Alpine ski
area, where the UV irradiance even on a horizontal surface may increase due
to reflection from snow by more than 10 percent. In contrast, in a street
canyon the irradiance on a horizontal surface is reduced to 30% in shadow
and to about 75% for a position in the sun.
Citation: Hess, M. and Koepke, P.: Modelling UV irradiances on arbitrarily oriented surfaces: effects of sky obstructions, Atmos. Chem. Phys., 8, 3583-3591, doi:10.5194/acp-8-3583-2008, 2008.