The equatorial thermostad and subsurface countercurrents in the light of the dynamics of atmospheric Hadley cells

The simple Held and Hou (1980) nearly inviscid model of the axisymmetric at mospheric circulation, rationalizing the existence of Hadley cells, Jet Str eams, and tropical homogenization of potential temperature and vorticity, i s adapted to the oceanic subthermocline region. The meridional profile of r adiative equilibrium temperature, which provides the driving in the atmosph eric case, is replaced, in the oceanic case, by the large-scale equatorial doming of the thermocline. The meridional structure of the equatorial therm ostad and the existence, at its poleward flanks, of eastward subsurface cou ntercurrents coincident with sharp potential vorticity gradients are thus e xplained via angular momentum redistribution by secondary ageostrophic over -turning cells in the meridional plane. Taking into account the existence o f the equatorial undercurrent within the thermocline has little effect on t he overall structure of the subthermocline solution at a given longitude, e ven though homogenization of properties is less efficient.