On the Effect of Sea Spray Evaporation on Tropical Cyclone Boundary-layer Structure and Intensity

Strong winds in a tropical cyclone over the ocean can produce substantial amounts of sea spray in the lowest atmospheric boundary layer by both bursting air bubbles in whitecaps and whipping spume from the tips of waves. Recent attention has been given to the quantitative evaluation of the effect of sea spray evaporation on both the intensification and intensity of tropical cyclones using numerical models, but contrast results have been reported regarding whether the maximum achievable intensity of a tropical cyclone can be affected by sea spray evaporation. In this study, a comprehensive diagnostics from sensitivity numerical experiments will be provided to elucidate possible physical processes that can affect tropical cyclone intensity due to the presence of sea spray evaporation. We will address how the sea spray evaporation affects the boundary layer structure, the transfer of energy to and from the ocean surface, the boundary layer thermodynamic budget, and the cloud processes. We find that although significant effects occur to all the above aspects, the maximum achievable intensity of a tropical cyclone is little affected. This is not sensitive to the model physical parameterizations. However, we find a considerable sensitivity of the intensification rate of the model tropical cyclone to model cloud microphysics parameterization, and the parameterization for sea spray evaporation.