A Theory of Equatorial Deep Jets*
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A simple linear theory of the circulation in a meridionally bounded equatorial ocean driven by density mixing localized near the eastern boundary is used to model the subthermocline circulation of the equatorial oceans. The mixing is modeled by a specified, spatially limited source term in the density equation. The theory is for a steady circulation, and the model, which is continuously stratified, contains simple linear drag laws for frictional dissipation and a similar, linear damping for density anomalies. The model employs Gill’s formulation of the basic linear equations near the equator. The satisfaction of the condition of zero zonal flow at both bounding meridians requires the determination of the amplitude of the Kelvin component (or its steady counterpart) by an integral condition over the domain of the flow. When that condition is satisfied, the solution, for reasonable settings of the parameters, naturally yields an alternating array of zonal currents localized within a deformation radius of the equator. An essential condition for the appearance of this high vertical mode zonal structure is the localization of the forcing to the eastern boundary and to a small vertical region at the top of the domain, which is identified with the mixing occurring at the base of the equatorial thermocline.