Intercomparison of a Regional Climate Model Ensemble for Selected European Catchments

ABSTRACT

Understanding regional hydroclimatic variability and its drivers is essential to anticipate the impacts of climate change on water resources and sustainability. Yet, considerable uncertainty remains in the simulation of the coupled land–atmosphere water and energy cycles, largely due to structural model limitations, simplified process representations, and insufficient spatial resolution. Within the framework of the Collaborative Research Centre 1502 (CRC1502), this study presents a coordinated intercomparison of regional climate model simulations designed for water cycle process analysis over Europe. We analyse the performance of simulations using the ICON and TSMP1 model systems and covering the period 1990–2020, comparing against reference datasets (E‐OBS, GPCC, and GLEAM). We focus on 2‐m air temperature, precipitation and evapotranspiration over four representative basins—the Ebro, Po, Rhine, and Tisa—within the EURO‐CORDEX domain. Our analysis reveals systematic cold biases throughout most of Europe, with ICON generally outperforming TSMP1. ICON simulations exhibit heterogeneous performance in precipitation biases, with less overestimation than TSMP1, but still reflecting the persistent challenge of accurately simulating precipitation. TSMP1 and ICON generally agree on positive ET biases in southern and western Europe and negative biases in the north and east, with TSMP1 showing greater local differences than ICON. Sensitivity experiments using higher‐resolution sea surface temperature forcing data produced comparable performance among themselves; however, they outperformed the other models in simulating precipitation over the Ebro and Rhine basins across most seasons. ICON simulations at 3 km resolution further indicate that the inclusion of irrigation improves the representation of summer temperature and precipitation in the Po basin. This baseline evaluation provides a first assessment of the CRC1502's multi‐model ensemble and highlights key structural differences that influence model behaviour across hydroclimatic regimes.