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Tropical fingerprints on the polar mesosphere

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If you have a question about this talk, please contact Tracy Moffat-Griffin.

Open to non-BAS people, please contact Tracy Moffat-Griffin on 221566 or tmof@bas.ac.uk if you wish to attend

An analysis of 11 years of horizontal wind data derived from meteor wind observations from a SuperDARN radar at Halley, Antarctica shows clear evidence of a quasi-biennial modulation of the high latitude southern hemisphere semidiurnal tide in the upper mesosphere. The tide is enhanced when the equatorial stratospheric QBO above 10 hPa is in the westerly phase. This enhancement is greatest in the summer time when the S=1 non-migrating component is known to dominate the semidiurnal wind field at high latitudes, and is coincident with an enhancement of the summertime planetary wave activity in the upper mesosphere. These results strongly support the hypothesis that the S=1 component of the semidiurnal tide observed at high latitudes is due to a non-linear interaction between the migrating S=2 semidiurnal tide and quasi-stationary S=1 planetary waves, the propogation of which is dependent on the critical level filtering driven by the equatorial QBO .

This talk is part of the British Antarctic Survey series.

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