Representation of Snow Cover in the EURO-CORDEX Regional Climate Model Ensemble – Evaluation of Current State and Future Projection

Abstract:

Snow cover is a key-component of the climate system in high latitude regions, areas with temperate climate and alpine areas. Its occurrence distinctively modulates physical surface properties such as albedo and heat conduction, which might strongly influence the atmosphere through feedback processes. In addition, snow cover has a high socio-economic relevance – e.g. for hydropower production (water storage on intra-annual scales), ski tourism, road traffic and natural hazard management. The interaction of snow coverage and climate can be studied with a comprehensive set of models, which range from GCMs with coarse spatial resolution (~200 km) and typically rather simple snow cover parameterization schemes to land surface models with high resolution (~100 m) and very sophisticated treatments of snow. In this study, we evaluate output from the EURO-CORDEX project, which among others provides an RCM ensemble at a horizontal resolution of ~12 km. Coarser-scale features of typical mountain ranges are represented at this resolution while the model domain is large enough to investigate snow cover on a European scale. Besides, we investigate four regions (Alps, Scandinavia, Pyrenees and Carpathians) with particularly interesting snow characteristics in more detail. In a first step, we evaluate present-day snow cover in 11 ERA-Interim driven RCMs with various reference data (reanalysis, land surface models and remote sensing). The evaluation suggests that the RCMs are generally able to reproduce the spatio-temporal characteristics of European snow coverage. Nevertheless, certain RCMs indicate substantial biases, particularly in mountainous regions where snow water equivalent is often overestimated. The evaluation further indicates that certain reference datasets might suffer from similar uncertainties than the RCMs, which complicates bias quantifications. In a second step, we analyse the projected future change of snow cover for three greenhouse gas scenarios RCP2.6, RCP4.5 and RCP8.5. In Europe at the end of the 21st century the loss of snow covered area is most pronounced for RCP8.5 in the Pyrenees and Alps below 1000 m. In Scandinavia snow cover reductions are less pronounced. Overall, the projected loss of snow covered area decreases with height and latitude.