Coupled Atmosphere–Ocean Wave Simulations under High Wind Conditions

Abstract

The impact of ocean surface waves on the structure and intensity of three tropical cyclones and a topographically forced bora event is investigated using a coupled atmosphere?ocean wave modeling system. The coupled system is capable of representing surface momentum fluxes that are enhanced due to young ocean waves in fetch-limited conditions, which yield surface roughness lengths that significantly depart from the conventional Charnock-type formulation. In general, the impact of ocean-wave-induced stress on the tropical cyclone central pressure was quite variable with ocean wave feedback resulting in changes ranging from 8 hPa deeper to 3 hPa shallower. The increased low-level stress due to the ocean waves reduced the near-surface winds by 2?3 m s?1, with local differences in excess of 10 m s?1, which directly led to a 10% reduction in the significant wave height maxima. The reduced significant wave heights in the coupled model were in closer agreement with observations for Tropical Cyclone Bonnie than for the uncoupled model. The tropical cyclone tracks were generally insensitive to ocean wave feedback effects. The boundary layer structure was found to be generally insensitive to large roughness enhancements associated with coupled ocean wave feedbacks for topographically forced high wind phenomena, such as the bora.