MODES OF INTERANNUAL VARIABILITY IN THE STRATOSPHERE

During 1964-91, stratospheric temperature and circulation in northern hemisphere winter varied interannually on time scales from 2 to approximately 12 years. A substantial percentage of December-February (DJF) interannual variance was correlated with the quasi-biennial oscillation (QBO). Additional monthly variance could be accounted for by quasi-decadal oscillation and QBO/low-frequency modulation. The QBO was the largest and most consistent of these signals, and its decadal modulation explains an apparent correlation with the solar cycle depending on the sign of the QBO - an interpretation supported by principal component analysis.