Fully Coupled High-Resolution Atmosphere-Ocean-Wave Simulations of Hurricane Henri (2021): Implications for Offshore Load Assessments

Abstract. This study presents a fully coupled modelling system that integrates atmospheric, ocean, and wave models to simulate interactions during tropical cyclones and assess their implications for offshore infrastructure. The system is evaluated using Hurricane Henri (2021), chosen for its distinctive track along the U.S. northeast coast, an area with densely populated regions and offshore wind energy zones. The event is supported by extensive observations, including airborne Doppler radar, dropsondes, sea surface temperature, and ocean surface wave measurements. Three experiments with increasing complexity in atmosphere-ocean-wave coupled processes are conducted to examine their impact on storm intensity and development. Compared to atmospheric-only and atmosphere-ocean coupled simulations, the fully coupled model reduces intensity overestimations and improves the wind structure from near the surface to the upper troposphere. These improvements are due to realistic representation of complex feedback loops between the atmosphere, ocean, and waves. Wave-induced cooling of sea surface temperatures and reduced surface enthalpy flux mitigate intensity overestimation. Additionally, wave-driven surface roughness, reflected in realistic surface roughness length and drag coefficients, enhances the radial and vertical profiles of hurricane boundary layer winds. The fully coupled simulation shows promising potential for assessing risks to offshore infrastructure, featuring a more stable atmospheric boundary layer, weaker surface roughness, and lower turbulent kinetic energy. These factors allow wind veer to persist and align more closely with observations. The system also captures wind-wave misalignment, emphasizing the importance of incorporating ocean and wave components for accurate risk assessments in offshore infrastructure, such as wind turbine operations.