Abstract
From an earlier study of the longitudinal evolution of the equatorial zonal momentum balance in a nonlinear stratified simulation of the Atlantic equatorial undercurrent it was shown that the annual mean simulated undercurrent reaches its maximum zonal velocity as it emerges from an accelerated deep inertial regime extending over about 15 degrees of longitude off the western boundary. Further east, frictional forces overcome the accelerating effect of the zonal pressure gradient form and the undercurrent keeps losing eastward momentum as it flows eastward. If the accelerating deep western regime extended over a wider range of longitudes the maximum emerging velocity would be larger. This is shown to occur in a nonlinear stratified simulation of the Pacific equatorial undercurrent because the western Pacific thermocline is thicker due to the basin size and to the longitudinal structure of the zonal winds. This is offered as an explanation for the larger observed zonal velocities of the Pacific undercurrent.
