Interdependence of the tropical and extratropical QBO: relationship to the solar cycle versus a biennial oscillation in the stratosphere

Interannual variations in the tropical and polar stratosphere are investigated in monthly mean records of north polar temperature and equatorial zonal wind. The spectrum of polar temperature possesses discrete components associated with the tropical quasi-biennial oscillation (QBO), as well as with a biennial oscillation (BO) that figures prominently in the record of north-polar temperature. The BO, in fact, accounts for as much temperature variance as the QBO. The running correlation between equatorial zonal wind and polar temperature oscillates on a decadal timescale, resembling the 11-year sunspot cycle [Kodera, 1993]. This oscillation is shown to follow from an interaction between the QBO and the BO. Interaction between the QBO and BO also figures in Labitzke and van Loon's [1988] evidence of the solar cycle, which results when data are stratified according to the QBO. Both apparent signatures of solar cycle influence therefore revolve about the interpretation of the BO.