Collaborative Research: Ocean Horizontal Array Turbulence Study: an investigation of Subfilter-Scale Fluxes in the Marine Surface Layer

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OHATS (Ocean Horizontal Array Turbulence Study ) is a novel field program to examine air-sea interaction and in particular the coupling of surface-layer turbulence in the marine (atmospheric) boundary layer with the underlying surface waves. These wind-generated waves influence the dynamics of the marine surface layer and the air-sea fluxes of momentum and scalars. The ability to model the marine surface layer reliably with large-eddy simulation (LES) is unknown. LES and in particular its sub-filter-scale (SFS) parameterization require validation against and guidance from observations for this complex flow. The critical piece of the project is a field campaign specifically directed at the measurement of SFS variables in the marine surface layer. These observations will be used to elucidate the impact of waves and atmospheric stability on surface-layer turbulence and provide a database to validate and improve SFS models for LES. OHATS will be carried out in the summer of 2004 at the recently constructed Air-Sea Interaction Tower (ASIT) located off the coast of Martha's Vineyard. The ASIT is connected directly to shore via the Martha's Vineyard Coastal Observatory (MVCO) operated by Woods Hole Oceanographic Institution. OHATS will employ 14 sonic anemometers in a two-level setup similar to the Horizontal Array TurbulenceStudy done in California in 2000. SFS velocity and temperature fluxes will be deduced by spatially filtering the measured 3-D velocity and temperature fields. Simultaneous observations of the wave-field properties will be made in order to establish correlations with the SFS variables. OHATS will enhance the current understanding of air-sea interaction processes, provide insight into the couplings between surface waves and turbulence, and shed new light on SFS modeling for LES A graduate student will work on the project along a postdoctoral student from the Advanced Study Program at NCAR.. The project will provide hands-on experience and training with a fundamental problem in air-sea interaction research, i.e., the coupling of wind and waves to graduate student and post-doc. The data will be made available to the broader community via the internet.