Unravelling drivers of the future Mediterranean precipitation paradox during cyclones

In recent years, the Mediterranean region has experienced intense cyclones with heavy precipitation, resulting in severe flooding with multiple fatalities and significant damage to infrastructures. Additionally, the basin is increasingly recognized as a climate change hotspot. For these reasons, it is fundamental to understand how Mediterranean cyclones respond to climate change, identifying the key processes driving these changes.

Our study is the first combining CMIP6 models with a high-resolution atmosphere-ocean coupled regional climate model (AORCM) over the Mediterranean to investigate how changes in moisture advection and surface diabatic processes influence precipitation during intense cyclones under three SSP scenarios (SSP5-8.5, SSP2-4.5, SSP1-2.6). The AORCM is the only available with three SSP scenarios for the Mediterranean basin and it is essential for identifying the physical mechanisms driving cyclone-related precipitation changes. Despite a strong reduction in the number of intense cyclones and a subsequent decline in seasonal precipitation, our results underscore a significant increase in cyclone-related extreme precipitation, especially under the SSP5-8.5 scenario. The AORCM shows that this intensification is driven by enhanced moisture exchange from the ocean to the atmosphere and increased mid-level moisture transport toward the coastal regions of Southern France, Italy, and the Balkans.

These results offer valuable information for regional climate impact assessments in the Mediterranean basin and provide novel insights into the physical processes driving precipitation changes. The analysis underscores the potential risk of more damaging inland flooding in a warming climate, particularly in southern Spain and France (including their islands), the Italian Peninsula, the Balkan region and the Levantine Coast, posing severe issues for such densely populated areas. Besides, our results highlight the importance of combing different models within coordinated frameworks to disentangle the influences of large-scale forcings and regional climate processes on the future Mediterranean climate under varying radiative forcing levels. This approach is crucial for improving confidence in climate projections.