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High-Latitude Mesospheric Bore Event Observed Over Antarctica

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Taylor et al.[1995] observed a spectacular short-period mesospheric gravity wave event during the ALOHA-93 campaign. The event consisted of a sharp front in the airglow brightness that was accompanied by several trailing small-scale waves. Dewan and Picard [1998] classified this event to be the first observation of a mesospheric bore event.

All-sky observations of short-period mesospheric gravity waves have been made from Halley Station, Antarctica (76°S, 27°W) to investigate their climatology. On 27 May, 2001, an unusual wave event exhibiting several features characteristic of a "bore" were observed near simultaneously in the OH, Na, and O2 nightglow emissions. Mesospheric bores are relatively rare wave events that have previously only been observed at mid- and low-latitudes. Novel analysis of this polar latitude event has yielded several very interesting features:

  • The bore initially appeared as a single, high contrast, linear front, accompanied by a sharp enhancement in intensity in all three nightglow emissions.
  • A number of trailing wave crests were observed to form within the instruments field of view (500x500 km) with a high growth rate of 6.6 waves/hour.
  • The wave pattern exhibited most unusual dynamics with significant variability in the observed wave phase speed and a marked reduction in the horizontal wavelength by ~50% over a 1-hr period.
  • The derived group speed approached zero in near coincidence with a strong acceleration of the background wind field (measured by radar) strongly suggesting this was a breaking wave event.


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