Evaluation of the elevation dependence of climatic indices from EURO-CORDEX regional climate models in the Alpine region

Climate change is a global phenomenon with regionally varying peculiarities and sensitivities. Mountainous regions have been found to be particularly sensitive and prone to severe impacts. At local scale the complex orography determines a range of climate change impacts that often depend on elevation which makes the future projection of the evolving mountain environment even more complex. Although regional climate models can solve the atmospheric equations on very fine scales, simulated climatic patterns can show large differences when compared with observations due to morphology and topography of the territory which, if complex, do not allow the models to explicitly resolve all the processes at that local scale. Studying the impact of climate change as a function of elevation is therefore unreliable if models fail to capture local physical mechanisms or large scale elevational patterns. In this study we aim to evaluate the representativeness of historical climate simulations in function of the elevation over the European Alps by using the EURO-CORDEX ensemble of regional climate models at 0.11° resolution. In addition to evaluating the standard EURO-CORDEX model output we assess the impact of bias-adjustment as represented by the CORDEX-Adjust ensemble in historical periods and for several climatic indices. The model data are compared to high-resolution observational datasets over the entire Alpine region and to national observational datasets. We identify potential advantages and weaknesses of bias-adjustment methods depending on elevation, region, and climatic index. Based on the results, we can put estimates of future climate change elevation patterns into context, evaluating which are the most appropriate indices for studies including climate change adaptation in mountain regions, and defining physical mechanisms at play at different elevations.