Evaluation and Comparison of CMIP6 Global Climate Model Historical Simulations Against ERA5 Reanalysis for Mediterranean Cyclone Tracking

Abstract

The weather and climate of the Mediterranean region are highly influenced by mid-latitude cyclones, i.e., Mediterranean cyclones. The accurate simulation of these systems is crucial for preparing for future climate change. This study evaluates the ability of 12 global climate models (GCMs) within the Coupled Model Intercomparison Project Phase 6 (CMIP6) to reproduce historical (1979–2014) spatial distribution, intensity, and seasonal cycle of Mediterranean cyclones against ERA5 reanalysis data. The results provide historical performance context for the interpretation of future projections. Cyclones are detected using an objective algorithm based on mean sea level pressure, which has a temporal resolution of 6-h, and a spatial resolution of 1°. The results demonstrate that although there is a systematic underestimation of cyclone numbers compared to the reference, GCMs reproduce regions with high cyclone frequencies relatively well. The accuracy of spatial patterns of frequencies shows seasonal differences: simulation results perform better during winter (when deeper cyclones occur), while summer performance is weaker. These seasonal and spatial differences also appear when analyzing selected focus regions, where GCMs struggle to consistently capture local seasonal cycles. This might be caused by a shift in the spatial placement of cyclones in the GCMs that highlights the need for higher resolution models when focusing on subregions.