Sea spray effects on the air-sea fluxes at moderate and high wind speeds

At sufficiently high wind speed conditions, in the presence of breaking waves, the surface of the ocean separates to form a substantial number of sea spray drops, which can account for a significant fraction of the total air-sea surface area and thus make important contributions to the air-sea fluxes of momentum and heat. Ultimately, the spray mediated fluxes depend on three controlling factors: the number and size of drops formed at the surface, the duration of suspension within the atmospheric marine boundary layer, and the rate of momentum, heat and mass transfer between the drops and the atmosphere. While the latter factor can be estimated from acknowledged theories, the estimates for the former two are not well established. Using a recent, sea state dependant physically-based model of the sea spray source function along with the results from Lagrangian stochastic simulations of individual drops, we estimate the aggregate spray-mediated fluxes for various wave-age conditions. We find reasonable agreement with existing models and estimates within the empirical range of wind speed conditions. At high wind speed conditions that are outside the empirical range, however, we find somewhat lower spray-mediated fluxes than previously reported in the literature, raising new questions about the relative air-sea fluxes at high wind speeds as well as the development and sustainment of hurricanes.