8.3
Impact of sea spray on air-sea fluxes: a physical model
James A. Mueller, Univ. of Delaware, Newark, DE; and F. Veron
The surface area of sea spray, relative to the air-sea interface, becomes sufficient at hurricane wind speeds for substantial spray-mediated momentum and scalar fluxes, specifically those of heat and moisture. At high winds, the larger drops presumably dominate the spray-mediated fluxes due to their relative volume. The wind not only strips and forms more spume drops from the top of wave crests with increased forcing, but it also suspends larger drops for longer periods of time. Ultimately, the spray-mediated fluxes depend on two controlling factors, the number and size of drops formed at the surface as well as the duration of suspension within the atmospheric, marine boundary layer. Due to significant variation between previous studies, this presentation freshly addresses both of these controlling factors.
We begin with a derivation of a new physically-based spume generation function to find the drop distribution at the surface. Unlike most previous studies, both the magnitude and shape of this generation function change with wind forcing and sea-state. In addition to reasonable agreement between this spume generation function and the limited data available, we find a potential explanation for the vast drop size differences among previous spume generation studies through a distinction between formed and suspended drops. To calculate the duration of suspension and mean air-drop fluxes, we employ a Lagrangian model to track individual droplets from ejection into the air to ocean reentry or quasi-equilibrium. With this model, we find somewhat different suspension times and individual drop fluxes when solving the full microphysical and transport equations simultaneously. Because of the relative suspension time, the aggregate spume drop fluxes only become significant for intense wind forcing.
Session 8, Sea-Surface Physics, Including Waves, Whitecaps, and Aerosol Generation: Part 1
Wednesday, 14 January 2009, 8:30 AM-9:45 AM, Room 128A
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