Validation of CM SAF SARAH solar radiation datasets for Switzerland

The CMSAF SARAH dataset is currently the only publicly solar radiation dataset with a spatial resolution of 0.05 degree and an hourly temporal resolution covering Switzerland over a time period of more than 30 years. The dataset has a higher bias in mountainous regions. Large parts of Switzerland, especially in the Jura and Alps, are mountainous. We compared the daily global and diffuse irradiance with measured irradiance data of ground stations at different elevations. The mean absolute bias increases with higher elevation. We investigated the correlation of the elevation of buildings with the error of the ground stations. Stations below 1000 meter elevation have an average mean daily bias of -0.18 ± 8.54 W/m2 representing 87% of Swiss building footprints.