Gravity Wave-Induced Perturbations in Lidar Backscatter Profiles above La Réunion (21°S, 55°E)

Atmospheric gravity waves (GWs) play a crucial role in vertically coupling the lower and upper atmosphere, significantly impacting middle atmosphere dynamics. Despite their importance, accurately representing GWs remains a persistent challenge for numerical weather prediction and global atmospheric models.

Atmospheric particulate matter or aerosols present in both the troposphere and the stratosphere are deeply involved in radiative processes and atmospheric chemistry. A strong interplay exists between GWs and aerosols, particularly in the formation and evolution of cirrus clouds. Furthermore, aerosol-induced warming processes can also generate GWs within the atmospheric boundary layer, especially over polluted tropical cities. The dynamics of the aerosol vertical distribution can, in certain cases, serve as tracers for GWs, particularly during intense aerosol mixing driven by strong meteorological events in the troposphere and stratosphere.

This study examines GW-induced perturbations in lidar backscatter profiles observed above the Maïdo Observatory at La Réunion (21°S, 55°E) on the night of November 21, 2023 near the southern subtropical barrier.  Complementary data from lidar-based temperature and wind measurements, radiosondes, COSMIC-2 satellite observations, and ERA5 reanalysis confirm key GW characteristics in the mid-troposphere. These include a vertical wavelength of 5-6 km, an observed period of approximately 24 hours, an downward phase propagation, and an upward energy propagation into the stratosphere.