The Frequency-Dependent Response and Asymptotic Properties of Turbulent Mixing in the Upper Ocean.

摘要

The underlying purpose of this research was to understand and predict the response of upper ocean boundary layer mixing to high frequency oscillations in the atmospheric forcing attributable to the diurnal heat flux cycle, unsteadiness in the wind, and other short term changes. To accomplish this task, a non-stationary, one-dimensional bulk model of the mixed layer originally proposed by Garwood (1976, 1977) is generalized by deriving a new equation for the entrainment buoyancy flux which includes the unsteady term. To examine the importance of the unsteady term, a reduced form of the turbulent kinetic energy equation is solved numerically. The results predict the high frequency cutoff above which the unsteady term should not be neglected. The quasi-steady state assumption is accurate only for low frequency forcing up to this cutoff. The results of this research provide a theoretical basis for realistically applying the mixed layer models to ocean boundary layer problems on all time scales.