Air–sea interaction in medicanes with atmosphere–ocean–wave coupled regional climate simulations

Medicanes (Mediterranean hurricanes or cyclones with tropical-like characteristics) have a significant impact on coastal areas and small islands in the Mediterranean region. However, the underlying mechanisms, particularly the role of the air–sea interaction for medicanes, are not fully understood. To investigate these mechanisms, we use the ERA5 reanalysis product as well as four high-resolution simulations conducted with the Regional Earth System Model (RegESM) to study 16 medicane events for the period of 1979–2012 over the Med-CORDEX (Mediterranean-Coordinated Regional Climate Downscaling Experiment) domain. The RegESM model is run in standalone atmosphere, standalone wave, atmosphere–ocean, and atmosphere–ocean–wave settings. Overall, all model settings are able to simulate 15 out of 16 medicane cases compared to the reference ERA5. For most cases, the standalone atmosphere is sufficient to simulate most of the medicane characteristics. However, the analysis shows that the atmosphere–ocean–wave setting improves the storm intensity, while the standalone atmosphere setting tends to show too high wind speeds for the medicanes. For some medicanes, the atmosphere–ocean setting increases the sea surface temperatures, fostering evaporation. This enhanced evaporation contributes to the formation of convective systems by increasing the latent heat flux. Additional wave coupling improves the spatial extent and the timing of the observed medicanes. Due to improved simulation of roughness length over water and its interaction with the atmospheric boundary layer, winds are improved in some cases, leading to a better eyewall at the center of the medicane.