Investigation of Gravity Waves over four Antarctica stations using M-transform method

Using data from All-Sky OH Imagers located at four Antarctic stations—Rothera (Lat. 67.6°S, Long. 68.1°), Halley (Lat. 75.6°S, Long. 25.5°W), Davis (Lat. 68.6°S, Long. 78.0°E), and McMurdo (Lat. 77.8°S, Long. 166.7°E)—which are part of the Antarctic Gravity Waves Instrument Network (ANGWIN) international project, we investigated mesospheric small scale gravity waves. First, we selected only clear sky ("clean window") data for at least 2-hour periods using a machine learning method. This method has an accuracy of approximately 92%, validated using two years of Rothera data, improving on the previous manual selection. Then, we investigated the gravity waves using the M-transform method. This FFT-based technique showed the distribution of gravity wave power in function of phase velocity and direction of propagation. To estimate the principal directions of propagation, we computed the cumulative sum in all directions at 1-degree intervals. Based on this method, the main direction was determined for each day and for each month, showing the small-scale gravity wave variability through the Austral winter around the Antarctic Continent.