Intellectual Merit: This project consists of analytical, computational and observational components. It features a new theoretical basis for three-dimensional, numerical ocean models conjoined with surface wave models. Nevertheless, additional empirical rules such as those extant in turbulence closure schemes and prominent in the modeling of surface boundary layers are needed. The marriage of surface layer (or mixed layer) models and surface wave models poses new questions and requires new thinking and data. It is expected that many of the unknowns can be addressed by detailed measurements only available in a laboratory setting as described below, thence on to available field data. First, a circulation model for mean properties dependent on one horizontal and one vertical dimension (essentially a channel or wave tank flow) will be set up together with a surface wave model. The model will encompass Stokes drift, vertically dependent wave radiation stress terms and other processes and will require a new critical look at means of representing turbulence mixing. There will be a need to distinguish between total momentum input from wind and that portion which contributes to wave buildup or wave decay. Bottom boundary layer - wave interaction will also be a component of the overall model.
The laboratory experiments will be designed to test critical aspects of the model, in particular those processes that involve interactions between wave induced motions and turbulent flow. The existing laboratory tank and measuring equipment is well suited to examine: a) the characteristics of mechanical (paddle) or wind-generated waves; b) turbulent flow in a 2-D slice, usually a plane normal to the cross-tank axis, c) fine scale structure of the turbulence including direct estimates of the rate of kinetic energy dissipation; d) turbulent velocities and pressure above the surface and estimates of the momentum transfer from wind to waves; e) methods of separating the flow variables into their mean, wave-related and turbulent parts.
The anticipated results of this research will be a combined three-dimensional, current-wave-turbulence model which includes sub-models for wind forcing, surface wave breaking, bottom friction and other empirical ingredients supported by data obtained from the proposed experiments and data available in the oceanographic literature. The model will be a precursor to wave dependent air/sea transfer of climate relevant gases.
Broader Impacts : This new model will have many broader impacts within the research community. The Princeton Ocean Model developed by Dr. Mellor and colleagues has been applied worldwide to understand the dynamics of many diverse oceanographic systems. The development of advanced community models such as those proposed here that deal with wave dynamics and the interactions of waves and turbulence, are essential building blocks for fully coupled atmosphere-interface-ocean models. Such models are necessary for understanding and predicting such important environmental processes as: pathways and accumulation of anthropogenic pollutants, climate change and the spread or extinction of marine species. The results from both the modeling and experimental components of this research will be available at a dedicated web site. This will provide the broader community with up-to date information on the progress of the research. Final results will be disseminated through refereed publications as the extensive track record of the investigators demonstrates. Additional impacts of the research will be through graduate student support and the improved capabilities of the Air-Sea Interaction Salt-water Tank (ASIST) facility at the University of Miami. ASIST is an excellent tool for instruction in wind-wave-current interaction at all levels. A laboratory course that demonstrates basic principles of wave theory and boundary layer turbulence has been developed at the University of Miami. The facility has also sponsored summer internships from several institutions including the French Naval Academy and the University of Toulon. Given the success of these projects we expect to continue to provide internship opportunities. Community outreach has been a significant ongoing activity at ASIST. Many campus and community groups will continue to be introduced to wind/wave interaction studies through tours of the facility.
