A novel joint space-wavenumber analysis of an unusual Antarctic gravity wave event

As part of a collaborative research program between British Antarctic Survey, U.K. and Utah State University, USA, all sky airglow images were recorded at Halley Station Antarctica (75.5 S, 26.7 W). An unusual mesospheric gravity wave event was observed in the OH nightglow (nominal height ≈87 km) over a period of ≈3 hours on the 27–28 May, 2001. The characteristics of the bore wave event were determined by application of the one dimensional spatial S-Transform analysis. This is the first time such analysis has been performed on airglow data. By employing these local spatial spectral analysis, the evolution of the wave packet can be measured. The wave parameters (phase velocity, wave number, wavelength, period) were inferred from as little as 2 images (separated in time), which is a powerful ability when a data set of images is irregularly sampled in time, as is often the case in airglow imager studies. Several interesting and novel results were obtained regarding the dynamic evolution of the wave. The horizontal wavelength of the bore wave packet was seen to decrease as the packet evolved. Coincident with this observation, the horizontal phase speed decreased, with an associated decrease in wave packet amplitude.