This award will support continued collaborative research between a group of U.S. physical oceanographers led by Dr. Edward Monahan, Marine Sciences Institute, University of Connecticut and French colleagues led by Dr. P.G. Mestayer, Institut de Mecanique Statistique de la Turbulence, Marseille, France. The research project, entitled "CLUSE HEXIST 3" is an outgrowth of the international cooperative program HEXOS (Humidity Exchange over the Sea), which aims to understand the humidity transfer processes from sea to atmosphere during gale and storm wind events, with a special emphasis on the role of marine sprays. One major effort in the HEXOS program is centered around the construction of realistic numerical models of the coupled transfer processes within the lower boundary layer. Such models are viewed as essential in the evaluation of the impact of sea spray on the transfer process and as a guide in interpreting measurements. Within the context of the HEXOS program, a laboratory oriented subprogram, HEXIST, has been established. HEXIST, which stands for the HEXOS Experiments in the Simulation Tunnel, is intended to take advantage of the unique capabilities of the Large Air-Sea Interaction Simulation Tunnel of the Institut de Mecanique Statistique de la Turbulence in Marseille. The transfer processes of heat, water vapour and spray-droplets will be controlled independently by means of the tunnel controls of wind speed, water, air and dew-point temperatures and by artificial aeration devices (spray bubblers). Thus, the tunnel measurements will provide a test bed for models that can eventually be extended to the open ocean. In this project, U.S. and French researchers will have the opportunity to design a new approach to laboratory studies of spray droplet behavior using the Marseille facility. U.S. sensing technology and analysis capabilities will contribute to the joint project. Together with other coordinated elements of the HEXOS program, this series of experiments is the most comprehensive attack to date on the complex question of water exchange at the sea surface. The results of this research will have a major impact on advancing parameterization of the water exchange process. Improvements in the simulation of aerosol droplets will make the results of these experiments more directly relevant to the modelling of oceanic processes.
