Large-eddy simulation of interaction of ocean and atmospheric boundary layers

Abstract

We developed nonhydrostatic three-dimensional models of the ocean boundary layer and the atmospheric boundary layer, which can reproduce large-scale (comparable to mixed layers thickness) eddy structures induced by both thermal convection and surface wind stress. The models are integrated into a coupled model of interacting boundary layers. Interaction between the models is due to the exchange of momentum, heat and moisture fluxes through the water-air interface. When constructing the models we use the methodology of large-eddy simulation. It supposes that large-scale eddies which play a significant part in the momentum, heat and salinity (or moisture) transport inside the boundary layers are described explicitly. To take into account small-scale (with spatial scales smaller than the mesh size of the model) isotropic turbulence we use parameterizations relating the energy of sub grid motions to the characteristics of slower processes. The systems of differential equations in the models consist of the Reynolds-type equations for describing the evolution of momentum, heat and salinity (or moisture), the equation of incompressible fluid continuity, and equations of state for sea water and damp air. To close the system of equations we use additional evolution equations of the turbulent kinetic energy of small-scale eddies and the dissipation rate of turbulent energy. We carried out a number of numerical experiments with the obtained models in which we succeeded in reproducing the motions similar to eddies observed in the atmosphere and the ocean.