An Inertial Theory of the Equatorial Undercurrent

Abstract

An inertial nonlinear model of the equatorial undercurrent is presented. The model is a simple two-layer model whose lower layer represents the undercurrent. The flow in the lower layer preserves potential vorticity and Bernoulli function. The former includes the relative vorticity f the current and the latter includes the current's kinetic energy. The required relation between the potential vorticity and the Bernoulli function is determined by matching the solution far from the equator with the ventilated thermocline theory of Luyten et al. The model describes an eastward-accelerating undercurrent fed by a general wedge-shaped meridional circulation pattern. The general character of the meridional and zonal flow, as well as the magnitudes of the undercurrent velocity, the current width and thermocline depth agree reasonably well with observations.