ICON-waves: towards an atmosphere-waves coupled coupled operational system at DWD

Wind-driven ocean gravity surface waves affect basic physical processes such as heat, momentum, and mass exchange between the ocean and the atmosphere. Wind wave energy generates additional turbulence, modifies ocean currents, and controls the state of the sea surface. As of now, DWD's operational weather forecast system ICON-NWP does not explicitly account for ocean surface waves. Wave effects, for example, the effect on sea surface roughness, are represented by parameterisations based on local wind speed. However, the physics of the ocean-atmosphere interaction is more complex, and therefore methods of wave-spectrum-based coupling of atmosphere and ocean are necessary and have the potential for improving both weather and wave forecasts. To this end, in the framework of the Innovation Programme for Applied Research and Developments (IAFE) funded by the DWD, a new coupled ICON-NWP-waves system is currently under development. This project aims at using ICON's dynamical core and the wave spectrum physics from the wave model WAM, and will combine both into the new ICON-waves model. A parameterisation of sea surface roughness based on the wave spectrum will provide a two-way coupling mechanism at the ocean-atmosphere interface. The concept of ICON-waves, the current status of development as well as some preliminary results will be presented.