An Examination of Observed Southern Oscillation Effects in the Northern Hemisphere Stratosphere

Abstract

The effects of the Southern Oscillation on the December-February mean circulation in the Northern Hemisphere stratosphere were investigated using 34 years of data. No evidence for a significant relation between the Southern Oscillation (SO) and the zonally averaged flow is found for any region poleward of 20°N. The effects of the tropical quasi-biennial oscillation (QBO) on the zonal mean flow are much stronger, and this complicates the detection of 50 effects. Some more suggestive results are evident when hemispheric maps of height anomalies at 50 or 30 mb are composited for the warm extremes of the 50. The present findings are broadly consistent with earlier suggestions that, on average, the Aleutian high is intensified during the warm extremes of the Southern Oscillation. Even using the 34 years of data now available, however, the statistical significance of this relationship cannot be demonstrated unequivocally. Once again the separation of SO effects from QBO influences in the limited data available is a serious problem.