Coupling ocean currents and waves for seamless cross-scale modeling during Medicane Ianos

This study investigates the effects of a two-way wave–circulation coupled modeling framework during extreme weather events, with a particular focus on Medicane Ianos, one of the most intense cyclones to have occurred in the Mediterranean Sea. By utilizing a high-resolution unstructured numerical grid, the study explores wave–current interactions in both open-ocean and coastal environments. To this scope, we developed the first external coupler dealing with the SHYFEM-MPI circulation model and the WAVEWATCH III wave model. The interactions considered in this framework include sea-state-dependent momentum flux, radiation stress, Doppler shift, dynamic water depth for waves, and effective wind speed. The study adopts a rigorous validation of the formulations using idealized benchmarks tailored for these specific processes. Afterwards, the modeling framework was employed in real-case simulations of Medicane Ianos. The model is calibrated, and the ocean variables are rigorously validated against in situ and Earth observation (EO) data, including satellite-based measurements. The study found that wave-induced surge components contribute from 10 % to 30 % of the total water level during the storm and that sea-state-dependent momentum flux during a medicane can influence the vertical structure of the ocean up to 100 m. The accuracy of the wave model improves by around 3 % in terms of RMSE when coupled with a circulation model.