Poleward Flux of Atmospheric Angular Momentum in the Southern Hemisphere

Abstract

Tabulations of daily winds from IGY data were made at eight pressure levels (850, 700, 500, 400, 300, 200, 100 and 50 mb) for 121 Southern Hemisphere plus 22 Northern Hemisphere equatorial stations during the calendar year 1958, in order to study by seasons the poleward flux and convergence of relative angular momentum. The overwhelming importance in both seasons of the transports of relative angular momentum by the transient eddies is demonstrated. These transports are enough to balance the drain of atmospheric angular momentum in the belt of surface westerlies. The mean meridional motions and the standing eddies are ineffective in the fulfilment of the angular momentum balance requirements of this hemisphere. On the other hand the standing eddies are the main agents in the interhemispheric exchanges of relative angular momentum. There are insignificant seasonal variations in the vertically integrated horizontal momentum transport across latitude belts equatorward of 50S, although there is evidence for marked seasonal vertical fluctuations of the zones of maximum flux of relative angular momentum. The sign of the mean surface zonal stress computed from the angular momentum convergence is in good agreement with the distribution of the surface winds; the magnitude is comparable to that computed by Priestley (1951), except in the zones of strong surface westerlies.