Combining a ground-based UV network with satellite maps: A case study for Germany

A study for the comprehensive information of current UV exposure for the area of Germany, based on the method for near real time calculation of UV Index maps used in the framework of the Austrian UV Monitoring Network, is presented. For the area of Germany about 22.000 surface UV Index maps were calculated for the year 2022 via the radiative transfer model libRadtran by incorporating daily forecast data for ozone, albedo and aerosols from the Copernicus Atmospheric Monitoring Service and taking into account cloud information gathered from SEVIRI data of Meteosat Second Generation in the form of a cloud modification factor. Ground-based measurements of 17 stations of the German Solar Monitoring Network were then compared to the modelled maps. For most stations the correlation coefficient between measured and modelled UV Index (UVI) is above 0.92 and the mean difference of modelled UVI to measured UVI is smaller than 0.5 UVI. The modelling of the UVI at the high mountain station Schneefernerhaus is associated with higher uncertainties (correlation coefficient 0.85 and mean UVI difference 0.6 UVI) due to the small-scale topography with spatially highly variable albedo and clouds. Moreover, case studies for specific locations with respect to cloud conditions and topography are discussed, as well as a case study of the combination of ground-based measurements and modelled UVI maps in form of spatial correction factors.