The Large-Eddy Simulation (LES) model of Moeng (1984) for the turbulent atmospheric boundary layer has been adapted to ocean convection. Salinity has been added to the model code and a more realistic equation of state was included for simulations of deep ocean convection in the Mediterranean (Garwood, 1991) and polar seas (Isakari and Garwood,1993; Carsey and Garwood, 1993).

All LES models are nonhydrostatic and explicitly calculate the three-dimensional eddy field. However, in this model, the subgrid scale fluxes are parameterized with eddy viscosity, con ductivity and diffusivity which are time- and space-dependent and calculated by second order turbulence closure. Although the prognostic equations for eddy momentum, potential temperature and salinity are finite differenced in the vertical, the finest scale features of the turbulence in the equilibrium range of the spectrum are well resolved by use of pseudospectral representations in the horizontal.

Click here to see an animation of convection produced by the LES model in a 3.6-km cube driven by surface cooling of 200 watts/m/m. Blue is an isosurface of temperature that is .005C cooler than the mean. Green represents areas of downward vertical velocity exceeding10 cm/sec. The magenta surfaces are high dissipation zones, usually associated with high shear.

BIBLIOGRAPHY

Carsey, F. and R. W. Garwood, Jr., Geophys. Res. Lett., 20, 2207-2210,1993.

Garwood, R. W., Jr., Enhancements to deep turbulent entrainment, In Deep Convection and Deep Water Formation in the Ocean, ed., by P.C. Chu and J.C. Gascard, Elsevier, 189-205, 1991.

Garwood, R.W., Jr., S.M. Isakari, and P.C. Gallacher, Thermobaric Convection, in, The Polar Oceans and Their Role in Shaping the Global Environment, AGU Geophysical Monograph, 1994.

Isakari, S.M. and R.W. Garwood, Jr., Deep free convection in the Greenland and Mediterranean Seas, Poster and Video presented at Third Scientific Meeting of the Oceanography Society, Seattle, April 13- 16, p. 184, 1993.

Moeng, C.-H., A large-eddy-simulation model for the study of planetary boundary-layer turbulence, J. Atmos. Sci., 41, 2052-2062, 1984.