The European Space Agency's (ESA) Aeolus satellite mission is the first Doppler wind lidar in space, operating in orbit for more than 4 years since August 2018 and providing global wind profiling throughout the entire troposphere and the lower stratosphere. The Observatoire de Haute-Provence (OHP) in southern France and the Observatoire de Physique de l'Atmosphère de La Réunion (OPAR) are equipped with ground-based Doppler Rayleigh–Mie lidars, which operate on similar principles to the Aeolus lidar and are among essential instruments within the ESA Aeolus calibration and validation (cal/val) program. This study presents the validation results of the L2B Rayleigh clear horizontal line-of-sight (HLOS) winds from September 2018 to January 2022. The point-by-point validation exercise relies on a series of validation campaigns at both observatories: AboVE (Aeolus Validation Experiment), held in September 2019 and June 2021 at OPAR and in January 2019 and December 2021 at OHP. The campaigns involved time-coordinated lidar acquisitions and radiosonde ascents collocated with the nearest Aeolus overpasses. During AboVE-2, Aeolus was operated in a campaign mode with an extended range bin setting allowing inter-comparisons up to 28.7 km. We show that this setting suffers from larger random error in the uppermost bins, exceeding the estimated error, due to lack of backscatter at high altitudes. To evaluate the long-term evolution in Aeolus wind product quality, twice-daily routine Météo-France radiosondes and regular lidar observations were used at both sites. This study evaluates the long-term evolution of the satellite performance along with punctual collocation analyses. On average, we find a systematic error (bias) of −0.92 and −0.79 m s⁻¹ and a random error (scaled MAD) of 6.49 and 5.37 m s⁻¹ for lidar and radiosondes, respectively.

The mesospheric inversion layer (MIL) phenomenon is a temperature enhancement (10–50 K) in a vertical layer (∼10 km) lasting several days and spanning thousands of kilometers within the mesosphere. As MILs govern the mesospheric variability, their study is crucial for a better understanding of the middle‐atmosphere global circulation. MIL phenomenon is also important for applications in aeronautics as perturbations in the mesosphere are significant issues for the safe reentry of rockets, space shuttles, or missiles. However, the description of this phenomenon remains incomplete, since no observations of MIL's effects on winds exist, hampering an understanding of the mechanisms responsible for their formation. This study investigates simultaneous wind‐temperature observations in the altitude range of 30–90 km during MIL events. Strong winds deceleration occurred in the same altitude range as the temperature inversion, confirming the role of gravity waves in MIL's formation mechanisms.

European Space Agency’s (ESA) Aeolus satellite mission is the first Doppler wind lidar in space, operating in orbit for more than three years since August 2018 and providing global wind profiling throughout the entire troposphere and the lower stratosphere. The Observatoire de Haute Provence (OHP) in southern France and the Observatoire de Physique de l’Atmosphère à La Réunion (OPAR) are equipped with ground-based Doppler Rayleigh-Mie lidars, which operate on similar principles to the Aeolus lidar, and are among essential instruments within ESA Aeolus Cal/Val program. This study presents the validation results of the L2B Rayleigh-clear HLOS winds from September 2018 to January 2022. The point-by-point validation exercise relies on a series of validation campaigns at both observatories: AboVE (Aeolus Validation Experiment) that were held in September 2019 and June 2021 at OPAR, and in January 2019 and December 2021 at OHP. The campaigns involved time-coordinated lidar acquisitions and radiosonde ascents collocated with the nearest Aeolus overpasses. During AboVE-2, Aeolus was operated in a campaign mode with an extended range bin setting allowing inter-comparisons up to 28.7 km. We show that this setting suffers from larger random error in the uppermost bins, exceeding the estimated error, due to lack of backscatter at high altitudes. To evaluate the long-term evolution in Aeolus wind product quality, twice-daily routine Météo-France radiosondes and regular lidar observations were used at both sites. This study evaluates the long-term evolution of the satellite performance along with punctual collocation analyses. On average, we find a systematic error (bias) of −0.92 ms^-1 and −0.79 ms^-1 and a random error (scaled MAD) of 6.49 ms^-1 and 5.37 ms^-1 for lidar and radiosondes, respectively.

The European Space Agency's Aeolus satellite, equipped with the Atmospheric LAser Doppler INstrument (ALADIN), provides near-global wind profiles from the surface to about 30 km altitude. These wind measurements enable the investigation of atmospheric dynamics, including gravity waves (GWs) in the upper troposphere and lower stratosphere (UTLS). This study analyzes ALADIN wind observations and ERA5 reanalysis by deriving GW kinetic energy (Ek) distributions and examining their temporal and spatial variability throughout the tropical UTLS. A prominent hotspot of enhanced GW activity is identified by Aeolus, migrating from the Indian Ocean in boreal summer to the Maritime Continent in boreal winter, closely matching outgoing longwave radiation minima and, thus, highlighting convective origins. Results show that ERA5 consistently underestimates Ek in convective regions, especially over the Indian Ocean, where conventional wind measurements are sparse. Additional comparisons with Global Navigation Satellite System Radio Occultation (GNSS-RO) measurements of GW potential energy (Ep) corroborate these findings and suggest a significant underrepresentation of convection-driven wave activity in reanalyses. A multi-instrumental exploratory analysis also allows one to verify the empirical grounding of the established Ek$/$ Ep ratio. By providing direct wind measurements in otherwise data-sparse regions, Aeolus offers a valuable dataset for evaluating and potentially improving the representation of GWs in reanalyses, particularly in remote tropical areas. The combination of Aeolus and GNSS-RO data allows for an observationally based examination of the partitioning between kinetic and potential energy, highlighting discrepancies with reanalysis products that could inform future model parameterization development.

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.