Mesospheric short-period gravity waves in the Antarctic Peninsula observed in all-sky airglow images and their possible source locations

Abstract

This study presents an analysis of OH airglow images observed from an all-sky camera (ASC) at King Sejong Station (KSS), Antarctic for the 2012？2016 period. The two- dimensional power spectra of short-period gravity waves (< 1 h) as a function of phase velocities are obtained using the M-transform method that employs the time sequence of ASC images. The amplitudes of the power spectral densities show that the mesospheric wave activity is the largest during winter (May, June, and July) and is the smallest in fall (February, March, and April). Wind-blocking diagrams are constructed on the same two-dimensional domain as in the two-dimensional spectra using horizontal winds obtained from MERRA-2 reanalysis at z = 0？80 km and from KSS meteor radar data at z = 80？90 km. Climatologically, the spectral regions of slowly propagating gravity waves (< 30 m s-1) are overlaid by the wind-blocking areas, which suggests the filtering of gravity waves with small phase speeds by winds below the upper stratosphere. Eastward propagating gravity waves in winter and intense south- eastward waves in spring (October) are found to be unfiltered by the stratospheric winds. It is also found from the spectral analysis that these unfiltered gravity waves can originate from the upper stratosphere or the lower mesosphere, and not from the troposphere, which suggests the possibility of ASC observation of the secondary gravity waves generated near the stratopause.