Summary
Observations and modelling described by Becker and Fritts [Ann Geophys, 24, 1175-1188, 2006] suggests that wintertime planetary wave activity, and the gravity-wave filtering associated with it, affect the global meridional residual circulation that drives the summer mesosphere from radiative equilibrium. This interhemispheric coupling between the winter stratosphere and the summer mesosphere has been further investigated in modelling studies and found to be consistent with northern hemisphere observations of polar mesospheric clouds [e.g. Karlsson et al., J. Atmos, Sol-Terr Phys., 71, 518-530, 2009]. Southern hemisphere stations have the advantage that the wintertime planetary-wave activity of their opposite hemisphere is of greater magnitude making an interhemispheric response likely. The 15-year set of radar observations of Mesosphere and Lower Thermosphere (MLT) winds obtained from Davis station in Antarctica (69S, 78E) has been used in a correlation analysis to identify northern winter atmospheric regions that are potentially coupled to the southern summer polar MLT. In this presentation, a dependence of this coupling on the QBO will be demonstrated. The response of the southern summer polar MLT to changes in winter stratospheric planetary wave activity has been shown to change sign according to the phase of the QBO. The current mechanism used to explain the coupling will be described and considered in the light of QBO modulation.