Medium-scale gravity waves observational methodology for antarctic airglow observations

Abstract. Medium-scale gravity waves are atmospheric waves with a horizontal scale of 50 to 1000 km. They can be observed via airglow all-sky images through the keogram technique. Our research introduces a novel algorithm that automatically identifies these waves, visible in airglow keograms, to study gravity waves over the Antarctic Peninsula. The all-sky airglow imager was installed at the Brazilian Comandante Ferraz Antarctic Station (EACF, 62° S), near the tip of the Antarctic Peninsula. The preprocessing techniques, including projection into geographical coordinates, flat fielding, consecutive image subtraction, and Butterworth filter, were used to enhance the visibility of the medium-scale waves. Based on the wavelet transform, the analysis procedure is used to identify the primary oscillation present in the keograms and reconstruct them posteriorly to check the wave coherency and obtain the wave parameters by fitting the phase lines in the phase domain. The fitting parameters then estimate wave parameters and the estimation quality. Simulations with synthetic images containing typical traveling waves were used to assess the error generated through the procedure and determine the fitting parameters threshold. This procedure was used to process a year of data in less than one hour, identifying most waves with errors below 5 percent. Waves observed parameters range close to the expected results, although they differ from other observation sites by having larger phase speeds and wavelengths.