ENERGETICS OF ENTRAINMENT ACROSS A DENSITY INTERFACE.

Abstract

A theory of the fluid entrainment rate into a turbulent, mixed layer across a horizontal density interface is presented. By integrating the turbulent kinetic energy equation over the depth of the mixed layer and assuming that turbulence dissipation rates are proportional to production rates, an equation is derived relating the potential energy change and entrainment rate to four major terms: (1) buoyant production of energy due to heating at the earth's surface; (2) mechanical production due to wind shear at the earth's surface; (3) mechanical production due to wind shear and dynamic instabilities such as Kelvin-Helmholtz waves at the inversion interface; and (4) energy losses due to internal gravity waves. It is shown that most previously published theories are just special cases of this more general energetics theory.