Parameterization of the Fair Weather Ekman Layer

Abstract

Most models of the upper ocean Ekman layer require a parameterization of turbulent mixing. Two very simple forms of parameterization are considered here and compared with fair weather data sets. A steady classical diffusion model is found to give reasonably good simulations with familiar values of diffusivity. However, the solutions show a systematic error in current direction that arises, apparently, from a non-parallel relation between shear and stress in the observed profiles.

Inspection of these and other data suggests that the transient, surface-trapped stratification associated with the diurnal cycle is likely to be important in fair weather conditions. The process of diurnal cycling can be treated in a layered model to yield a closed solution for Ekman layer currents. This solution has some of the characteristics of a useful parameterization for use in an OGCM, though it covers only a part of the relevant parameter range.