AIR-SEA EXCHANGE OF HEAT IN THE PRESENCE OF WIND-WAVES AND SPRAY

Waves extract a considerable part of the surface stress. While breakin g, they eject spray into the atmosphere. Spray evaporates and influenc es a balance of heat and moisture above the waves. A one-dimensional m odel of the stratified marine surface boundary layer (MSBL) accounts d irectly for the impact of waves on the momentum flux and the impact of sea spray on fluxes of heat and moisture. The model is viewed as a hi gher order parameterization of the MSBL compared to the bulk parameter ization. The model is based on the balance equations of momentum, the turbulent kinetic energy and the dissipation rate, heat, and moisture. A general experimental knowledge is used to parameterize the jet drop let concentration above the sea. That is, the surface droplet concentr ation is proportional to the cube of the friction velocity of the air, and the fast decay of droplet concentration with elevation above wave s is parameterized by exponential decay. The exchange coefficients for heat, moisture, and momentum are computed from the wind speed and the sea state. Consistency of the dynamical part of the model is checked against measurements of the drag coefficient. Consistency of the therm odynamical part is checked against measurements of the sensible heat f lux for light to moderate winds. The impact of spray is then assessed for stronger winds. It is shown that for a wind speed of about 25 m s( -1) and above the impact of sea spray on heat and moisture fluxes beco mes significant. The magnitude and the sign of the spray media,ted hea t and moisture fluxes depend on stratification of the atmosphere. To s ettle the issue whether or not sea spray plays an important role in ex change of heat and moisture above the sea, simultaneous direct measure ments of sensible heat and moisture flux under different stratificatio n conditions at wind speeds of about 25 m s(-1) are needed.