THE INFLUENCE OF THE QUASI-BIENNIAL OSCILLATION ON GLOBAL CONSTITUENTDISTRIBUTIONS

Long-lived stratospheric constituents observed by the Upper Atmosphere Research Satellite are compared between late northern winters 1991-19 92 and 1992-1993, The phase of the quasi-biennial oscillation (QBO) wa s such that the equatorial zonal wind was easterly (westerly) in the l ower stratosphere during the first (second) winter, In the tropics, wi nter-to-winter differences in the latitude-height distribution of zona lly averaged N2O and H2O are associated with differences in large-scal e upwelling, the QBO's mean meridional circulations, and lateral mixin g by incident extratropical Rossby waves. In the extratropics, signifi cant differences in zonally averaged N2O and H2O are also found which are believed to represent the extratropical constituent QBO, The trans port processes creating the extratropical constituent QBO are tentativ ely identified: In the winter extratropics, QBO modulation of the resi dual circulation appears to dominate in the upper stratosphere, while QBO-modulated Rossby-wave isentropic mixing dominates below about 10 m bar, Analysis of Rossby waves at low latitudes, as deduced from isobar ic constituent distribution maps, suggests that the meridional distrib ution of Rossby wave breaking depends on the tropical zonal winds, Eas terly QBO winds prevent Rossby-wave radiation into the tropics, so tha t a strong constituent concentration gradient is generated in the wint er subtropics, Westerly QBO winds allow some wave radiation into the t ropics, accompanied by isentropic mixing in the winter subtropics, cro ss-equatorial propagation, and occasional mixing in the summer subtrop ics. These effects depend on altitude and appear to vary in accord wit h the descending phases of the QBO.