Connection between the solar cycle and the QBO: The missing link

Evidence of the solar cycle in stratospheric polar temperature rests on a connection to the quasi-biennial oscillation (QBO) of equatorial wind. New evidence reported here establishes a mechanism for how the solar signature in polar temperature follows from the QBO, which itself is shown to vary with the solar cycle. Equatorial westerlies below 30 mb vary systematically with solar activity, as do equatorial easterlies above 30 mb. Changes in their duration introduce a systematic drift into the QBO's phase relative to winter months, when the polar vortex is sensitive to equatorial wind. Corresponding changes in the polar-night vortex are consistent with the solar signature observed in wintertime records of polar temperature that have been stratified according to the QBO.