Although the period of the equatorial stratospheric quasi-biennial osc
illation (QBO) is approximately 30 months, quasi-biennial modulation o
f the extratropical annual cycle may be expected to produce additional
spectral peaks at approximately 8.6 and 20 months in the extratropics
. Using Northern Hemisphere data for 1964-78 and global data for 1978-
93 it is shown that these spectral peaks are robust in both angular mo
mentum and Eliassen-Palm flux divergence. This spectral signature repr
esents a circulation anomaly in both hemispheres, and implies a dynami
cal origin to the previously observed similar spectral peaks in column
ozone in the extratropics.