A Quasi-equilibrium Turbulent Energy Model for Geophysical Flows

The Mellor-Yamada hierarchy of turbulent closure models is reexamined to show that the elimination of a slight inconsistency in their analysis leads to a quasi-equilibrium model that is somewhat simpler than their level 2½ model. Also the need to impose realizability conditions restricting the dependence of exchange coefficients on shearing rates is eliminated. The model is therefore more robust while the principal advantage of the level 2½ model, namely the solution of a prognostic equation for turbulent kinetic energy is retained. Its performance is shown to be not much different from that of level 2½.