THE SPRAY CONTRIBUTION TO NET EVAPORATION FROM THE SEA - A REVIEW OF RECENT PROGRESS

The part that sea spray plays in the air-sea transfer of heat and mois ture has been a controversial question for the last two decades, With general circulation models (GCMs) suggesting that perturbations in the Earth's surface heat budget of only a few W m(-2) can initiate major climatic variations, it is crucial that we identify and quantify all t he terms in that heat budget. Thus, here we review recent work on how sea spray contributes to the sea surface heat and moisture budgets. In the presence of spray, the near-surface atmosphere is characterized b y a droplet evaporation layer (DEL) with a height that scales with the significant-wave amplitude. The majority of spray transfer processes occur within this layer. As a result, the DEL is cooler and more moist than the atmospheric surface layer would be under identical condition s but without the spray. Also, because the spray in the DEL provides e levated sources and sinks for heat and moisture, the vertical heat flu xes are no longer constant with height. We use Eulerian and Lagrangian models and a simple analytical model to study the processes important in spray droplet dispersion and evaporation within this DEL. These mo dels all point to the conclusion that, in high winds (above about 15 m is), sea spray begins to contribute significantly to the air-sea fluxe s of heat and moisture. For example, we estimate that, in a 20-m/s win d, with an air temperature of 20 degrees C, a sea surface temperature of 22 degrees C, and a relative humidity of 80%, the latent and sensib le heat fluxes resulting from the spray alone will have magnitudes of order 150 and 15 W/m(2), respectively, in the DEL. Finally, we specula te on what fraction of these fluxes rise out of the DEL and, thus, bec ome available to the entire marine boundary layer.