MODELING THE EFFECTS OF BUOYANCY ON THE EVOLUTION OF GEOPHYSICAL BOUNDARY-LAYERS

A simple modeling based on the Imperial College k-epsilon turbulence description is shown to be capable of describing the highly anisotropic phenomena associated with the strong buoyancy effects encountered in upper ocean (and atmospheric boundary layer) environments. Both diurnal stratification and transition to buoyant mixing (from that driven by wind shear) are described in considerable detail, provided that the modeling of the turbulent Prandtl number and of the buoyant generation term in the epsilon model equation are evaluated in a suitably realistic and consistent way. The resulting model equations are suitable for simulating the evolution of the ensemble-averaged properties of the oceanic mixed layer in response to a specified history of interfacial shear stress and heat flux. The model is tested by comparing the predicted mixed layer evolution with the dissipation rate measurements of Shay and Gregg.