Aquatic Sciences Meeting, Albuquerque 2001

CS01 Air-Water Interactions

Date: Wednesday, February 14, 2001, Time: 3:45:00 PM

Location: San Miguel

Li, M, , Institute of Ocean Sciences, Sidney, Canada, lim@pac.dfo-mpo.gc.ca

CHARACTERIZATION OF WAVE-, SHEAR-, AND BUOYANCY-DRIVEN TURBULENCE IN THE OCEAN SURFACE BOUNDARY LAYER

Large Eddy Simulation (LES) models are usually run in dimensional units. The model results are either compared with a particular set of observations or explored by switching on and off different forcing terms in the governing equations. It is difficult to generalize these case studies into general parameterization schemes. In this paper we take a different approach by exploring LES results in nondimensional parameter space. We examine how thermal convection, shear instability and Langmuir circulation compete to generate turbulence in the ocean surface layer. Hoenikker number Ho (a ratio of buoyancy force to vortex force, Li and Garrett, 1995) and turbulent Langmuir number Lat (a ratio of the water friction velocity to the Stokes drift velocity, McWilliams et al., 1997) are identified as two controlling dimensionless parameters. We compare velocity and temperature fields between flows at different parts of the parameter space. In particular, we examine how the low-order turbulence statistics such as vertical momentum and heat fluxes, velocity and temperature variances change as the parameters vary. Wave-driven Langmuir circulation dominates the turbulence field if Ho<1 and Lat is small. Shear-driven turbulence dominates if Lat is large and Ho is small. When Ho is large, however, buoyancy-driven convective turbulence dominates regardless of the values of Lat. We discuss preliminary model results for constructing a regime diagram in Ho - Lat space that can differentiate shear-, wave- and buoyancy-driven turbulence over a wide range of atmospheric forcing conditions.

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Aquatic Sciences Meeting, Albuquerque 2001

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