The dynamic vertical coupling in the middle and lower thermosphere (MLT) is documented over the Maïdo observatory at La Réunion island (21°S, 55°E). The investigation uses data obtained in the framework of the Atmospheric dynamics Research InfraStructure in Europe (ARISE) project. In particular, Rayleigh lidar and nightglow measurements combined with other observations and modeling provide information on a mesospheric inversion layer (MIL) and the related gravity waves (GWs) on 9 and 10 October 2017. A Rossby wave breaking (RWB) produced instabilities in the sheared background wind and a strong tropospheric activity of GWs on 9–11 October above La Réunion. The MIL was observed on the night of 9 October when a large amount of tropospheric GWs propagated upward into the middle atmosphere and disappeared on 11 October when the stratospheric zonal wind filtering became a significant blocking. Among other results, dominant mesospheric GW modes with vertical wavelengths of about 4–6 km and 10–13 km can be traced down to the troposphere and up to the mesopause. Dominant GWs with a wavelength of ~2–3 km and 6 km also propagated upward and eastward from the tropospheric source into the stratosphere on 9–11 October. Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperature and OH profiles indicate that GW activity in the middle atmosphere affects the upper atmosphere with waves breaking at heights below the MIL and in the mesopause. Several techniques are illustrated on nightglow images to access GW activity and spectral characteristics at the mesopause for high and low frequency GWs on the nights of 9–10 October. In conclusion, intense tropospheric activity of GWs induced by RWB events can be linked with MILs at the subtropical barrier in the South-West Indian Ocean during austral winter.

Extracting gravity wave (GW) perturbations from atmospheric observations relies on background removal techniques whose results may differ depending on the observational type and the spectral characteristics of the chosen method. This variability complicates the intercomparison of GW properties across instruments, sites, and studies. Nighttime averaging provides a simple estimate of the background but may smooth out smaller-scale structures. Spectral filtering enables targeted wavelength extraction, though it can be sensitive to noise and edge effects. Sliding polynomial fit offers flexibility but may suppress relevant signals depending on the polynomial degree. To address this issue, we implement and evaluate a processing method based on multiresolution analysis (MRA), designed to better extract and characterize the background and the multi-scale structures of GWs in lidar temperature and wind profiles. The MRA approach is then evaluated in comparison to these techniques and applied to lidar temperature and wind measurements collected on the night of 20 November 2023 at La Réunion. By decomposing the signal into dyadic vertical wavelength bands and an appropriate choice of corresponding details, the MRA can improve the detection of GW-induced perturbations in the spectral range of 0.8 to 12.8 km vertical wavelength by simultaneous background removal and denoising. We use the variance method as a benchmark for determining gravity waves potential energy (GWPE) and ask the question: “How well do the different filtering techniques compare with the variance method?” Given an overall agreement between our developped MRA and the variance method, we conclude that the MRA can also be used to determine reliable gravity wave kinetic energy (GWKE). Beyond energy estimation, MRA provides a unique capability to compute kinetic and potential energy profiles for tunable vertical wavelength bands, enabling the characterization of vertical and temporal evolution and interactions between different GW scales. These results establish MRA as a robust and complementary tool for improving GW analyses from lidar measurements, with promising applications to long-term climatologies and multi-instrument observational strategies.

This study introduces a processing method based on multi-resolution analysis (MRA) to characterize the multi-scale structures of gravity waves (GWs) with vertical wavelengths less than 13 km in lidar vertical profiles of temperature and wind in the middle atmosphere. The MRA approach is evaluated against conventional techniques, including polynomial fitting, spectral filtering, and nighttime temporal averaging, and applied to a case study of GWs observed on November 20, 2023. Among these methods, MRA demonstrates superior performance by enhancing the signal-to-noise ratio through signal decomposition and selective filtering. This targeted filtering improves the detection and extraction of GW-induced perturbations, particularly for dominant vertical wavelengths around 5 km. In terms of GW potential energy (GWPE), the MRA-based method yields values comparable to those derived from the variance method, except at the stratopause, where it estimates nearly twice the GWPE. However, the variance-based estimate remains within the MRA-derived confidence interval, indicating good agreement. In contrast, the Butterworth low-pass filter produces energy densities an order of magnitude higher than the variance method, suggesting possible overestimation of perturbation amplitudes. Polynomial fitting and nighttime mean methods appear insensitive to small-scale GW structures near the stratopause, where wave dissipation may occur. Beyond energy estimation, the MRA method offers a distinct advantage for analyzing GW propagation and scale interactions due to its multi-scale decomposition capability. It reveals GW features and structures that remain obscured by common techniques, establishing it as a valuable tool for advancing the study of GW dynamics in the middle atmosphere.

This study introduces a processing method based on multi-resolution analysis (MRA) to characterize the multi-scale structures of gravity waves (GWs) with vertical wavelengths less than 13 km in lidar vertical profiles of temperature and wind in the middle atmosphere. The MRA approach is evaluated against conventional techniques, including polynomial fitting, spectral filtering, and nighttime temporal averaging, and applied to a case study of GWs observed on November 20, 2023. Among these methods, MRA demonstrates superior performance by enhancing the signal-to-noise ratio through signal decomposition and selective filtering. This targeted filtering improves the detection and extraction of GW-induced perturbations, particularly for dominant vertical wavelengths around 5 km. In terms of GW potential energy (GWPE), the MRA-based method yields values comparable to those derived from the variance method, except at the stratopause, where it estimates nearly twice the GWPE. However, the variance-based estimate remains within the MRA-derived confidence interval, indicating good agreement. In contrast, the Butterworth low-pass filter produces energy densities an order of magnitude higher than the variance method, suggesting possible overestimation of perturbation amplitudes. Polynomial fitting and nighttime mean methods appear insensitive to small-scale GW structures near the stratopause, where wave dissipation may occur. Beyond energy estimation, the MRA method offers a distinct advantage for analyzing GW propagation and scale interactions due to its multi-scale decomposition capability. It reveals GW features and structures that remain obscured by common techniques, establishing it as a valuable tool for advancing the study of GW dynamics in the middle atmosphere.

The study investigates the vertical wave coupling from the Earth's surface to the middle atmosphere over the Maïdo Observatory at La Réunion (21°S, 55.5°E). Wind velocity and temperature profiles from the ground-based instruments, including the LiWind Doppler Rayleigh-Mie and Li1200 Rayleigh Lidars, in conjunction with other observations (radiosoundings, COSMIC-2 radio-occultation, SABER) and ERA5 reanalysis, are analyzed to characterize gravity waves (GW) and their vertical propagation during the period from November 20th to November 24th, 2023. Notably, a tropospheric subtropical westerly jet manifested above La Réunion during this period and jet instabilities contributed to enhance GW activity in the troposphere. Wavelet methods are employed for denoising purposes and for highlighting multiscale GW from raw wind and temperature profiles. In particular, our analysis reveals the existence of a GW with a 5-km vertical wavelength and approximately a 24-hour period, propagating upward from lower troposphere to the middle atmosphere above La Réunion’s Maïdo Observatory. Among others, the horizontal distribution of this structure surrounding La Réunion is examined using COSMIC-2 radio-occultation and SABER data. In addition, the ERA5 analysis also provides supporting evidence of such structures and GW filtering in the stratosphere.

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.