Climatology of short-period mesospheric gravity waves over Halley, Antarctica (76 S, 27 W)

We present a first detailed climatological study of individual quasi-monochromatic mesospheric, shortperiod gravity-wave events observed over Antarctica. The measurements were made using an all-sky airglow imager located at Halley Station (76S, 27W) and encompass the 2000 and 2001 austral winter seasons. Distributions of wave parameters were found to be similar to findings at other latitudes. The wave headings exhibited unusually strong anisotropy with a dominant preference for motion towards the Antarctic continent and a rotation from westward during fall, to poleward in mid-winter, to eastward in spring. This rotation was accompanied by a systematic increase of 50% in the magnitudes of the horizontal wavelengths and observed phase speeds. It is postulated that the observed wave anisotropy was due to a succession of wave sources of different characteristics lying equatorward of Halley, or a dominant source mechanism evolving with time during the winter months.