1Institute for Meteorology, University of Natural Resources and Applied Life Sciences (BOKU), Vienna, Austria
2Institute for Geography and Regional Research, University of Vienna, Vienna, Austria
3Division for Biomedical Physics, Innsbruck Medical University, Innsbruck, Austria
4Institute of Geophysics, Polish Academy of Sciences, Warsaw, Poland
5Division for Medical Physics and Biostatistics, Veterinary University Vienna, Vienna, Austria
*now at: Institute for Atmospheric and Climate Science, ETH Zurich, Zurich, Switzerland
Abstract. The aim of this study is the reconstruction of past UV-radiation doses for two stations in Austria, Hoher Sonnblick and Vienna, using a physical radiation transfer model. The method uses the modeled UV-radiation under clear-sky conditions, cloud modification factors and a correction factor as input variables. To identify the influence of temporal resolution of input data and modification factors, an ensemble of four different modelling approaches has been calculated, each with hourly or daily resolution. This is especially important because we found no other study describing the influence of the temporal resolution of input data on model performance. Following the results of the statistical analysis of the evaluation period the model with the highest temporal resolution has been chosen for the reconstruction of the UV-radiation doses. This model (HMC) uses modelled UV-radiation under clear sky conditions, a cloud modification factor, both with hourly resolution, and a monthly correction factor. A good agreement between modelled and measured values of erythemally effective irradiance was found at both stations. In relation to the reference period 1976–1985 an increase in erythemal UV-irradiance in Vienna of 11 percent is visible in the period 1986–1995 and an increase of 17 percent in the period 1996–2005 can be seen. At Hoher Sonnblick an increase of 2 percent has been calculated for the yearly averages in erythemal UV for the period 1986–1995 and an increase of 9 percent for the period 1996–2005 in comparison to the reference period. For the different seasons the strongest increase in erythemal UV radiation has been found for winter and spring season at both stations.