Characteristics of mesospheric gravity waves over Antarctica observed by ANGWIN (Antarctic Gravity Wave Instrument Network) imagers using 3-D spectral analyses

Takashi S. Matsuda, Graduate University for Advanced Studies, Tachikawa, Japan
Takuji Nakamura, Graduate University for Advanced Studies, Tachikawa, Japan
Mitsumu K. Ejiri, Graduate University for Advanced Studies, Tachikawa, Japan
Masaki Tsutsumi, Graduate University for Advanced Studies, Tachikawa, Japan
Yoshihiro Tomikawa, Graduate University for Advanced Studies, Tachikawa, Japan
Michael J. Taylor, Utah State University
Yucheng Zhao, Utah State University
Pierre-Dominique Pautet, Utah State University
Damian J. Murphy, Australian Antarctic Divistion, Kingston, Tasmania, Australia
Tracy Moffat-Griffin, British Antarctic Survey, Cambridge, UK


We have obtained horizontal phase velocity distributions of the gravity waves around 90 km from four Antarctic airglow imagers, which belong to an international airglow imager/instrument network known as ANGWIN (Antarctic Gravity Wave Instrument Network). Results from the airglow imagers at Syowa (69°S, 40°E), Halley (76°S, 27°W), Davis (69°S, 78°E), and McMurdo (78°S, 167°E) were compared, using a new statistical analysis method based on 3-D Fourier transform (Matsuda et al., 2014) for the observation period between 7 April and 21 May 2013. Significant day-to-day and site-to-site differences were found. The averaged phase velocity spectrum during the observation period showed preferential westward direction at Syowa, McMurdo, and Halley, but no preferential direction at Davis. Gravity wave energy estimated by I′/I was ~5 times larger at Davis and Syowa than at McMurdo and Halley. We also compared the phase velocity spectrum at Syowa and Davis with the background wind field and found that the directionality only over Syowa could be explained by critical level filtering of the waves. This suggests that the eastward propagating gravity waves over Davis could have been generated above the polar night jet. Comparison of nighttime variations of the phase velocity spectra with background wind measurements suggested that the effect of critical level filtering could not explain the temporal variation of gravity wave directionality well, and other reasons such as variation of wave sources should be taken into account. Directionality was determined to be dependent on the gravity wave periods.