VERTICAL MIXING AND CABBELING IN LAYERED MODELS

A consistent scheme for vertical mixing in layered numerical models is derived in this paper. The fact that the vertical coordinate (density ) depends on the properties being transported (namely salinity and pot ential temperature) renders the inclusion of vertical mixing in layere d models a subtle problem. The approach the authors have taken is base d upon the entrainment into a layer being proportional to the turbulen t activity in that layer. Across each interface there are then two ent rainment velocities, one upward velocity that is the entrainment of fl uid into the layer above the interface, and one downward velocity, bei ng the entrainment velocity into the layer below the interface. This d ouble entrainment accounts for both the diffusive and the advective co nsequences of turbulent mixing. The proposed scheme works without appr oximation for a nonlinear equation of state and can readily handle the production of density caused by cabbeling. Several examples are given .