QBO effects on Antarctic mesospheric winds and polar vortex dynamics

A dynamical link is demonstrated between the equatorial quasi-biennial oscillation (QBO) and high-latitude mesospheric zonal winds recorded by an Imaging Doppler Interferometer (IDI) at Halley, Antarctica. Above ~80 km eastward winds in winter (an extension of the polar vortex into the mesosphere) are strengthened under easterly 50 hPa QBO conditions. This is similar to the Holton-Tan effect in the stratosphere but working in opposition. The weak winter time zonal winds are shown to differ by up to 2.6 m/s dependent on QBO phase. In spring, zonal winds are most strongly correlated with the equatorial 25 hPa QBO and are significantly more westerly in November, an extension of the QBO response in the stratosphere below. It is suggested that QBO modulation of the vortex winds in the Antarctic mesosphere is dependent on planetary-wave activity from the Antarctic in winter and Arctic in spring.

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