Statistical Analysis of Mesospheric Gravity Wave Intensity, Propagation Directions, and Blocking Characteristics, over four Antarctica stations from 13 years of All-Sky OH imager data

Using 13 years of All-Sky OH Imagers data obtained at four Antarctic stations - McMurdo (77.8°S, 166.7°E), Rothera (67.6°S, 68.1°W), Halley (75.6°S, 25.5°W) and Davis (68.6°S, 78.0°E) - the propagation direction, one of the key parameters of mesospheric small-scale gravity waves (GWs), was analyzed. To identify the main propagation direction, the M-transform - adopted as the standard gravity wave analysis technique within the Antarctic Gravity Waves Instrument Network (ANGWIN) international project - and a numerical method were used. The results reveal a dominant anti-clockwise directionality around the Antarctic continent. Since this outcome is likely imputable to blocking effects due to the strong wind associated with the polar vortex, we investigated the effects of the background wind using the JAWARA re-analysis dataset, which fully covers Antarctica and the atmosphere up to ~140 km. Overall directionality of the background winds shows an opposite direction to the waves’ propagation, although the blocking effect for each day does not perfectly matched, which suggests the presence of secondary waves, or ducted waves. In addition, the monthly results from April to September (Austral Winter) show that the GW intensity tended to increase toward the middle of the winter at all four stations. The yearly results indicate a dramatic increase in GW intensity around 2013 at Davis station. As part of the ANGWIN project, this study provides the first consistent analysis of small-scale gravity wave data from four Antarctic stations over one solar cycle.