Antarctic Gravity Waves: Energy and Spectral Baselines from 30-100 km using 14 years of McMurdo Lidar Observations to investigate Vertical Coupling Processes

McMurdo, Antarctica is a hotspot of gravity wave (GW) activity which has been monitored by the McMurdo Lidar campaign consistently since 2011, enabling numerous GW discoveries such as that of persistent GWs in the middle and upper atmosphere, secondary wave generation in the middle atmosphere, coupling between the equatorial QBO and Antarctic GW energies, and many others. After 14+ years of lidar data collection, baselines of GW parameters are developed in order to investigate and characterize the typical spectral and energy characteristics of these GWs. Rayleigh scattering signals are analyzed to form 4-season baselines from 30-70 km, and resonance fluorescence of atmospheric metal layers are used to assess baseline winter GW activity in the mesosphere and lower-thermosphere (MLT) from 80-100+ km. These baselines are formed using newly-developed interleaved data processing methods which enable bias/noise-floor-free estimation of GW energy and spectra, increasing the accuracy and reliability of the derived parameters. Importantly, these methods enhance vertical coupling studies by extending the vertical limit of observable middle-atmosphere GW parameters upwards by an additional 20 km.
The middle atmosphere and MLT GW potential energy, vertical wavenumber, and temporal spectral baselines are investigated to determine how Antarctic GWs evolve from the stratosphere to the MLT, where many of these parameters are assessed bias-free or otherwise for the first time in the MLT. The comparison of middle atmospheric baselines with those of the MLT provides insight into vertical coupling processes such as wave breaking/dissipation and secondary/tertiary wave generation as these combined baselines provide a comprehensive picture of how Antarctic GW energy and spectra develop from 30 to 100+ km.
Additionally, this study explores newly observed, regularly occurring wave-dissipation features in the middle atmosphere which are found in these Lidar-derived baselines. These features can be seen in previous Antarctic observations but have never before been noted or studied. The dissipation trends are investigated using the McMurdo lidar observations and GW resolving atmospheric models to determine their extent, cause, and implication for wave breaking and vertical coupling schemes.