Benchmarking Across Scales: Evaluating EURO-CORDEX CMIP6 Regional Climate Models over Germany

The Climate Evaluation and Quality Assessment for Reliability (CL3AR) is DWD's comprehensive and integrated quality assessment framework for regional climate simulations. As the demand for reliable high-resolution climate data grows, CL3AR serves as a critical bridge between raw model output and actionable climate services. The framework employs a multi-scale approach that evaluates model performance across a hierarchical spectrum: it combines the assessment of global teleconnections with the analysis of European-scale synoptic circulation patterns and fine-scale regional similarity metrics for key climate variables.

In this study, results from an ensemble of more than 20 regional climate simulations produced in the EURO-CORDEX framework are presented. To ensure a robust validation, model outputs are  compared against a variety of high-quality reference data, including global and regional reanalysis datasets as well as high-resolution gridded observations. The evaluation focuses on a suite of essential climate variables critical for impact modeling and climate adaptation, specifically 2m temperature, precipitation, surface wind speed, and global shortwave radiation. By analyzing these variables, CL3AR identifies model strengths and systematic biases.

Following the evaluation phase, the framework incorporates a post-processing pipeline where bias-adjustment and further statistical downscaling are performed. These steps are essential to fulfill the requirements of stakeholders within the German domain, extending to the hydrological scale by including the transboundary river catchments of neighboring countries. Ultimately, CL3AR provides consistent, quality-controlled reference ensembles based on the latest EURO-CORDEX CMIP6 simulations. These ensembles serve as a foundational dataset for climate adaptation strategies, urban planning, and water management in Germany, ensuring that local decisions are supported by the highest standard of regional climate science.