The mean meridional circulation of the southern hemisphere inferred from momentum and mass balance

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Abstract
The mean meridional circulation for the southern hemisphere is inferred from momentum and mass balance considerations. Recent calculations by Obasi of the transient eddy transports of momentum and the mean zonal flow are the only data used. The vertical eddy transports are taken into account only in the surface layers, where the stress is assumed to decrease linearly with pressure from its surface value. The surface stresses themselves are calculated from the pressure integral of the momentum equation, and by a short iteration process the effect of horizontal transport of momentum by the mean meridional circulation is taken into account. The resulting circulation is self consistent, needing only very small corrections to eliminate mass “drifts” across latitude circles, contrary to most direct measurements. The characteristic three cell pattern is very evident. The circulation is compared to that found in a somewhat similar manner by Mintz and Lang for the northern hemisphere. The winter circulations are found to be rather similar, but the polar direct cell is much stronger in the southern hemisphere. In the summer season the southern hemisphere circulation is much stronger. The kinetic energy balance for the southern hemisphere is briefly considered. Given our assumptions about the vertical eddy fluxes of momentum, about half the kinetic energy fed into the mean flow by the horizontal transient eddies is extracted by the mean meridional motion. The other half is dissipated near the surface. In each season, energy balance is achieved to within 3%, verifying the consistency of the calculations. DOI: 10.1111/j.2153-3490.1965.tb01419.x