Global Patterns of the Quasi-biennial Oscillation in Total Ozone

Kenneth P. Bowman Department of Atmospheric Sciences, University of Illinois at Urbana–Champaign, Urbana, Illinois

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Abstract

Nine years of total ozone measurements from the Total Ozone Mapping Spectrometer (TOMS) on Nimbus 7 are used to study the global structure of the quasi-biennial oscillation (QBO) in total ozone. Interannual variability of total ozone near the equator (10°S to 10°N) is dominated by the QBO. The equatorial ozone anomalies are independent of season and are well correlated (r > 0.8) with the equatorial zonal wind. In both hemispheres midlatitude anomalies are two to three times larger in winter than in summer. Global patterns of the ozone QBO are identified by computing lagged correlations between the zonal-mean equatorial ozone and ozone elsewhere on the globe. Correlations between equatorial and extratropical ozone are weak during the summer season (r ∼ 0) and large and negative during the winter (r < − 0.8 in the Southern Hemisphere and r − 0.6 in the Northern Hemisphere). There are nodes or phase shifts in the correlation patterns at ±10° latitude, at 60°S, and at 50°N. Large negative correlations extend to the poles in both winter hemisphere There are indications of a correlation between wave activity, as measured by the eddy variance of the total ozone field, and the QBO, although the variability of the eddy activity is large and the sample size is small. The correlations support the accepted view that equatorial ozone anomalies result from vertical transport by the QBO circulation. The correlation patterns do not support the theory that extratropical ozone anomalies on the QBO time scale are the result of either advection of equatorial ozone anomalies by the climatological circulation or quasi-horizontal mixing of the equatorial anomalies by planetary waves. Instead, the ozone anomalies resemble a seasonally modulated standing oscillation, possibly resulting from quasi-biennial wave forcing of the planetary-scale mean meridional circulation and the associated vertical advection of ozone.

Abstract

Nine years of total ozone measurements from the Total Ozone Mapping Spectrometer (TOMS) on Nimbus 7 are used to study the global structure of the quasi-biennial oscillation (QBO) in total ozone. Interannual variability of total ozone near the equator (10°S to 10°N) is dominated by the QBO. The equatorial ozone anomalies are independent of season and are well correlated (r > 0.8) with the equatorial zonal wind. In both hemispheres midlatitude anomalies are two to three times larger in winter than in summer. Global patterns of the ozone QBO are identified by computing lagged correlations between the zonal-mean equatorial ozone and ozone elsewhere on the globe. Correlations between equatorial and extratropical ozone are weak during the summer season (r ∼ 0) and large and negative during the winter (r < − 0.8 in the Southern Hemisphere and r − 0.6 in the Northern Hemisphere). There are nodes or phase shifts in the correlation patterns at ±10° latitude, at 60°S, and at 50°N. Large negative correlations extend to the poles in both winter hemisphere There are indications of a correlation between wave activity, as measured by the eddy variance of the total ozone field, and the QBO, although the variability of the eddy activity is large and the sample size is small. The correlations support the accepted view that equatorial ozone anomalies result from vertical transport by the QBO circulation. The correlation patterns do not support the theory that extratropical ozone anomalies on the QBO time scale are the result of either advection of equatorial ozone anomalies by the climatological circulation or quasi-horizontal mixing of the equatorial anomalies by planetary waves. Instead, the ozone anomalies resemble a seasonally modulated standing oscillation, possibly resulting from quasi-biennial wave forcing of the planetary-scale mean meridional circulation and the associated vertical advection of ozone.

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