Accurate detection of precipitation on a global scale is essential for advancing our understanding of the hydrological cycle and improving climate models. This study evaluates the performance of the Rain Masking Algorithm (RMA), developed for NASA's Micropulse Lidar Network (MPLNET), in detecting rainfall events and distinguishing them from non-rain events over multiple years. The RMA's effectiveness was validated against data from co-located disdrometers at two distinct MPLNET sites: the Goddard Space Flight Center (GSFC) in the United States and Universitat Polit & egrave;cnica de Catalunya (UPC) in Barcelona, Spain. Comparisons were also conducted with precipitation retrievals from the Integrated Multi-Satellite Retrievals for GPM (IMERG) project. Results indicate that the RMA is highly effective at detecting rain events, outperforming IMERG in sensitivity and accuracy at both sites, and demonstrating also unique capability in distinguishing virga, precipitation that evaporated before reaching the ground (not considered in the intercomparison). However, the algorithm shows limitations in identifying low-intensity precipitation and occasionally records false positives due to transient atmospheric artifacts. These results underscore the potential of the RMA in advancing the validation of satellite precipitation data from the ground, which is advantageous for the upcoming ESA-JAXA EarthCARE mission. Although the current analysis does not include EarthCARE data, we present the performance of RMA and a corresponding matchup strategy that are intended to facilitate next validation efforts for EarthCARE's precipitation data. This work also highlights the RMA as a promising tool for refining global precipitation monitoring and advancing meteorological and climate forecasting accuracy.

The Atmospheric LIDar (ATLID) instrument of the ESA's Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) satellite mission launched in May 2024 provides high-resolution vertical profiling of aerosols and clouds at 355 nm. Fully operational since July 2024, ATLID has been witness to a significant perturbation of stratospheric aerosol budget following the eruptions of Ruang volcano (Indonesia) in late April 2024. Using ATLID together with limb-viewing satellite instruments (OMPS-LP and SAGE III), we quantify the stratospheric aerosol perturbation generated by the Ruang eruption and characterize the global transport of volcanic aerosols. To evaluate the ATLID performance in the stratosphere, its data are compared with collocated ground-based lidar observations at various locations in both hemispheres and overpass-coordinated balloon flights carrying AZOR backscatter sonde. The intercomparison with suborbital observations suggests excellent performance of ATLID in the stratosphere and proves its capacity to accurately resolve fine structures in the vertical distribution of stratospheric aerosols. Using various satellite observations, we show that Ruang's eruptive sequence in April 2024 produced eruptive columns reaching 25 km altitude, and resulted in a doubling of the tropical stratospheric aerosol abundance for several months. The eruption timing in austral Fall and its high-altitude reach fostered efficient poleward transport into the southern extratropics during austral Winter 2024. By the time of the austral Fall 2025, the sulphate aerosols from Ruang have spread across the entire Southern hemisphere and were most probably entrained by the 2025 Antarctic polar vortex, potentially enhancing the polar stratospheric cloud occurrence.

Abstract. Stratospheric aerosol plumes from the 2022 Hunga eruption were observed by the first-ever ultraviolet (UV) 355 nm Doppler and High Spectral Resolution Lidar (HSRL) on board the European Space Agency’s Aeolus satellite. Independent measurement of extinction and co-polarized backscatter coefficients for particles are shown, capturing the Hunga plumes up to ≈ 28 km in altitude. Global map of L2A product are produced for latitudes band up to [35° S–10° N]. They are analysed with sulphur dioxide (SO2) concentration and sulfate aerosol (SA) optical depth (OD). A plume composed of optically thick patches with high SA OD above 0.025 is captured above 26 km in altitude. It exhibits high UV signal extinction up to 350 Mm⁻¹, scattering ratio (SR) up to 40, local optical depth (LOD) above 0.2, and lidar ratio (LR) above 100 sr. These SA long-lived patches are observed drifting south and transported west. Two branches separate by mid February 2022: a southern tale at ≈ 25 to 27 km in altitude around latitudes [30° S–15° S] and a northern tale at ≈ 23 to 25 km in altitude around latitudes [15° S–10° N]. The LR and LOD measured by Aeolus for the ageing branches reveal lower values below 80 sr and 0.04 respectively. A short-lived plume with low SA OD and high SO2 concentration is observed at lower altitudes ≈ 18 to 22 km with less strong UV scattering properties, and appears to disaggregate quickly.

Abstract. The WaLiNeAs campaign took place along the north-western Mediterranean coast between October 2022 and January 2023. This period was marked by unusual weather conditions associated with dry autumn and winter. In such conditions and for the first time, eight ground-based stations equipped with water vapour Raman lidars were strategically deployed by four European countries. We studied the consistency of this network with the water vapour mixing ratio (WVMR) products derived from the Infrared Atmospheric Sounding Interferometer (IASI) and the European Centre for Medium-Range Weather Forecasts (ECMWF) Reanalysis (ERA5), which assimilate IASI radiances. The statistical metrics used in the comparison are the mean bias (MB, defined as lidar – IASI or ERA5), the root mean square error (RMSE) and the correlation coefficient (COR). A positive MB of approximately 0.9 g kg−1 (respectively 0.6 g kg−1) between 0.2 and 5 km above mean sea level (amsl) indicates a systematic underestimation of the WVMR by IASI (respectively ERA5). RMSE values range from 1 to 2 g kg−1 across all lidar stations for IASI and ERA5, while the measurement uncertainties of the lidars are typically below 0.4 g kg−1. COR presents little variation between stations, it ranges from 0.7 to 0.8 and remains almost constant between 0.2 and 5 km amsl. Both the IASI and the ERA5 products appear to accurately reproduce the temporal variability of the vertical structure of water vapour in the low troposphere. Nevertheless, they show MB and RMSE significantly above the uncertainties of lidar measurements.

Abstract. Biomass burning (BB) aerosols emitted over Southern Africa (SAF) and South America (SA) represent a major seasonal perturbation to the usually pristine atmosphere of the South-West Indian Ocean (SWIO) but remain understudied in this remote region. Following a multi-instrumental approach, we characterize BB plumes reaching Reunion Island (21° S, 55° E) during September 2017, combining ground-based measurements (sun-photometer, lidars, Fourier Transform Infrared spectrometer), spaceborne observations, CAMS EAC4 reanalysis, and the Lagrangian transport model FLEXPART. Aerosol optical depth at 550 nm over Reunion reached unusually high values (0.16–0.42) during the second half of September, with organic matter contributing up to 60 %. MODIS imagery revealed two large-scale smoke plumes originating from SAF and SA transported toward the SWIO, and CALIOP profiles showed smoke layers extending from 4 to 9 km of altitude above Madagascar. On September 19th, a single layer was identified over Reunion between 2.8 and 4.7 km with an Ångström exponent (Å₃₅₅/₅₃₂) of 1.32±0.23, consistent with moderately aged BB particles essentially originating from SAF. On September 25th, two vertically decoupled layers were identified: a lower layer (3.3–5 km, Å=1.45±0.12) associated with mixed aged aerosols of SAF and SA origin, and an upper, drier layer (5–9 km, Å=1.60±0.06) of potentially fresher SAF smoke, consistent with rapid convective uplift into the mid-troposphere. This study offers new insights concerning the dynamical processes that govern aerosol variability over Reunion Island and highlights its value as a strategic long-term observational site in the SWIO.

The dust direct radiative effect (DRE) in the long-wave (LW) (DRELW), and the net effect (DRENET), is analysed during an intense and long-lasting Saharan dust intrusion over the Iberian Peninsula, complementing the study on the short-wave (SW) DRE (DRESW) (L & oacute;pez-Cayuela et al., 2025). In LW, a warming effect at both the bottom-of-atmosphere (BOA) and the top-of-atmosphere (TOA) levels is induced by the fine (Df) and coarse (Dc) dust particles, while Dc being dominant. The DRELW-to-DRESW ratio for Df ranged 4 %-8 % at BOA (1 %-4 % at TOA), and for Dc it was rather higher (39 %-54 % at BOA and 20 %-50 % at TOA). DRENET was consistently negative (net cooling) at both levels, and the derived atmospheric DRENET was positive (net warming). The Df contribution to DRENET was 12 % (LW) and 30 % (SW). The SW aerosol heating rate (AHR) peaked at higher altitudes, inducing warming within the dust layer, than LW AHR (weaker cooling). Consequently, a net warming inside the dust layer was found, with potential cooling below and above. While SW dominates the net atmospheric warming, LW cooling partially mitigates it. As a novelty of this study, two methodologies for estimating DRE in both LW and net spectral ranges are compared. Differences in DRE between a classical approach considering total dust and an approach separating fine and coarse modes are analysed. DRELW (and DRENET) is underestimated (overestimated) by using the dust-mode separation approach in comparison to the classical one (no separation) when fine radii are lesser (greater) than a particular threshold (e.g. 0.1 & micro;m), revealing the particle size impact in DRELW. The dust-induced net effect is primarily driven by SW and modulated by LW. The classical (no separation) approach overestimates DRENET, with mean (standard deviation) relative differences of - 5 % (7 %) at BOA and - 9 % (13 %) at TOA. Moreover, under moderate-to-high dust, separating Df and Dc contributions yields a weaker (stronger) net cooling at BOA (TOA).

Abstract. In a relatively recent paper by the authors, an explicit (i.e. non iterative) formula was provided for recovering the overlap factor in an aerosol lidar equipped with a N2/O2 Raman channel close to an elastic one to retrieve the aerosol extinction coefficient. One of the advantages of that formula is that it allows for the estimation of the impact of an erroneous lidar ratio in the retrieved overlap function. In the cited paper, the equation that relates the retrieved overlap function to the true one and the error on the assumed lidar ratio was given with almost no proof, on the grounds that its derivation was “boring and cumbersome, but otherwise straightforward”. After having discussed that equation with some interested researchers, it turns out that its derivation is not perhaps that straightforward. Therefore, we provide here its derivation. As a subproduct of that derivation, we propose a streamlined, two-step explicit formulation to retrieve the overlap function.

The TRANSAMA campaign (Transit to AMARYLLIS-AMAGAS oceanographic cruise), conducted aboard the research vessel Marion Dufresne II assessed instrument performance and investigated aerosol properties during its transit from La Reunion Island to Barbados (April-May 2023). A set of remote sensing instruments, including two CE318-T Sun-sky-lunar photometers and a CE370 single-wavelength elastic lidar, was deployed under the MAP-IO (Marion Dufresne Atmospheric Program-Indian Ocean) framework. Performance assessments of the deployed instrumentation support the development of coupled lidar-photometer systems for shipborne atmospheric observations, while acknowledging current detection limits. Synergistic observations provided vertically resolved aerosol properties, such as extinction coefficients, alongside atmospheric structure, highlighting the marine boundary layer (MBL) top at 800 +/- 300 m. While the photometer observations revealed clean atmospheric conditions over the South Atlantic (AOD440=0.08 +/- 0.04), thin aerosol layers above the MBL were identified as long-range transported residual biomass-burning-urban aerosols from Southern Africa with effective LR of 33 +/- 12 sr. Cloud layers covering a large range of altitudes (up to 16 km) were observed in 53 % of the lidar profiles, with a higher frequency at lower altitudes, where aerosol layers were more frequently detected. These findings emphasize the impact of continental aerosols on remote oceanic regions and demonstrate the capabilities of synergistic lidar-photometer measurements for advancing our understanding of aerosol variability, cloud formation, and climate processes over the oceans.

Upper troposphere (UT) humidity records are crucial for climate studies. Pseudo-monthly averaging limited just to nighttime measurement is applied to maximize temporal representativeness and enhance the lidar signal, providing WVMR profiles up to 16 km. This study evaluates 11 years (2013–2023) of water vapor mixing ratio (WVMR) profiles from a UV Raman lidar (Lid1200) at Réunion Island against MLS-Aura satellite retrieval, ERA5 reanalysis, and GRUAN-processed M10 radiosondes. The results show a systematic dry shift in MLS of up to 30% above 12 km, particularly during the wet season. Lidar exhibits a slight downward shift in WVMR, around 5% lower than ERA5 throughout the UT, with the largest deviations present above 14 km and greater variability during the wet season, Lidar calibration-related challenges during the dry season result in drier-than-ERA5 WVMR profiles (up to 10%). Additionally, comparisons with GRUAN-processed radiosonde reveal a substantial dry shift relative to the lidar, exceeding 30% above 12 km. We investigate the GNSS-based lidar calibration effect by applying an alternative calibration method. This produces higher WVMR values, revealing an ERA5 dry shift relative to lidar, increasing with altitude at the UT up to 25%. These measurements complement the global effort in monitoring and validating the tropical and subtropical upper tropospheric humidity.

ESA’s EarthCARE satellite mission launched in May 2024 and carrying Atmospheric LIDar (ATLID) provides high-resolution vertical profiling of aerosols and clouds at 355 nm. Fully operational since August 2024, ATLID has been witness to a significant perturbation of stratospheric aerosol budget following the eruptions of Ruang volcano (Indonesia) in late April 2024 as well as to a major panboreal outbreak of wildfire-generated pyrocumulonimbus (pyroCb) events in Canada and Siberia in late May 2025 that had a hemisphere-scale impact on stratospheric aerosol loading and composition. Using ATLID L1B data together with limb-viewing satellite observations (OMPS-LP and SAGE III), we quantify the stratospheric aerosol perturbations generated by these events, characterize the long-range transport of volcanic and smoke aerosols and contrast their optical properties and dynamical evolution. To evaluate the ATLID performance in the stratosphere, its data are compared with collocated lidar observations at various locations in both hemispheres and overpass-coordinated balloon flights in France carrying in situ aerosol sensors. The intercomparison with suborbital observations suggests excellent performance of ATLID in the stratosphere and proves its capacity to accurately resolve fine structures in the vertical distribution of stratospheric aerosols.ATLID observations of the global progression of volcanic and wildfire aerosols align closely with those from OMPS-LP and SAGE III, while uniquely providing continuous coverage through polar night. We show that Ruang aerosols were subject to an unusually massive isentropic transport into the southern extratropics and were most probably entrained by the 2025 Antarctic polar vortex, potentially enhancing the polar stratospheric cloud occurrence and Antarctic ozone hole.The stratospheric aftermath of the 2025 panboreal wildfire outbreak (POW) was characterized through a synergy of ATLID and ground-based lidar observations within ACTRIS and NDACC networks. The lidar measurements consistently report record-breaking values of stratospheric aerosol backscatter and AOD during the passage of the most intense Canadian pyroCb plume. This plume displayed a pronounced warm anomaly, linked to strong solar absorption by black carbon, and underwent diabatic self-lofting from ~13 km to 20 km altitude. ATLID further indicates that smoke aerosols dispersed across the northern extratropical stratosphere and may have penetrated into the tropics.

We assess the feasibility of correcting the aerosol optical depth by measuring an overlap function from the combination of elastic and N2/O2 rotational-spectrum Raman signals in an advanced aerosol lidar. It is shown that very similar overlap functions can be derived from measurements taken in different days, leading to an extension of minimum range at which the aerosol optical depth can be measured. This opens the way to determining the aerosol extinction coefficient at ranges below the lidar full overlap with overlap functions measured in favorable conditions.

Upper troposphere (UT) humidity records are crucial for climate studies. To maximize temporal representativeness and enhance the lidar signal, pseudo-monthly averaging—limited to nighttime measurement—is applied, yielding water vapor mixing ratio (WVMR) profiles up to 16 km. This study evaluates 11 years (2013–2023) of WVMR profiles from a UV Raman lidar (Li1200) at Réunion Island, comparing them with MLS-Aura satellite retrievals, ERA5 reanalysis data, and GRUAN-processed M10 radiosondes. The results reveal a systematic dry shift in MLS of up to 30% above 12 km, particularly during the wet season. The lidar exhibits a slight downward shift in WVMR, approximately 5% lower than ERA5 throughout the UT, with the largest deviations occurring above 14 km and greater variability during the wet season. Calibration-related challenges during the dry season result in lidar WVMR profiles that are up to 10% drier than ERA5. Additionally, comparisons with GRUAN-processed radiosondes show a substantial dry shift relative to the lidar, exceeding 30% above 12 km. We investigate the effect of GNSS-based lidar calibration by applying an alternative calibration method, which produces higher WVMR values. This reveals a dry shift in ERA5 relative to the lidar, increasing with altitude in the UT up to 25%. These measurements contribute to the global effort to monitor and validate tropical and subtropical upper tropospheric humidity.

Volcanic emissions from the Tajogaite volcano, located on the Cumbre Vieja edifice on the island of La Palma (Canary Islands, Spain), caused significant public health and aviation disruptions throughout the eruption (19 September-13 December 2021, officially declared over on 25 December). Nonetheless, it is considered the most significant volcanic event in Europe over the past 75 years due to the substantial amount of SO2 released into the atmosphere. The Instituto Geogr & aacute;fico Nacional (IGN), the authority responsible for volcano surveillance in Spain, implemented extensive operational monitoring to track volcanic activity and to provide a robust estimation of the volcanic plume height using a video-surveillance network. In parallel, the State Meteorological Agency of Spain (AEMET), in partnership with other Spanish ACTRIS (Aerosol, Clouds, and Trace Gases Research Infrastructure) members and collaborating institutions, conducted an unprecedented instrumental deployment to evaluate the impacts of this volcanic event on atmospheric composition. This effort included a network of aerosol profilers surrounding the volcano. A total of four profiling instruments were installed on La Palma: one MPL-4B lidar and three ceilometers. Additionally, a pre-existing Raman lidar on the island contributed valuable data to this study. These efforts are undertaken due to the importance of monitoring volcanic plume height in terms of air quality (necessary for the implementation of effective civil protection policies), volcanic activity surveillance (for tracking and forecasting eruptive behaviour), and, from a scientific perspective, for improving our understanding of the climatic and radiative impacts of this type of aerosol.In this study, the eruptive process was characterised in terms of the altitude of the dispersive volcanic plume (hd), measured by both IGN and AEMET-ACTRIS, and the altitude of the eruptive column (hec), measured by IGN. Modulating factors such as seismicity and meteorological conditions were also analysed. The consistency between the two independent and complementary datasets (hd,IGN and hd,AEMET) was assessed throughout the eruption (mean difference of 258.6 m).Our results confirmed the existence of three distinct eruptive phases, encompassing a range of styles from Strombolian explosive to effusive activity. While these phases have been characterised in previous studies, the results of the present work provide complementary information and novel insights from an alternative observational approach, which may be of use in future volcanic crises and will be applied to operational surveillance during such events.A subsequent comparison of hd,AEMET with the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) aerosol layer height product (ALHCALIOP) revealed a systematic underestimation by the satellite product, with a mean difference of 392.2 m.Finally, the impact of using hec in estimating SO2 emissions from the NASA MSVOLSO2L4 satellite-based product was evaluated. When a fixed (standard) plume altitude of 8 km was used instead of the observed hec, the total SO2 emission was significantly underestimated by an average of 56.2 %, and by up to 84.7 %. These findings underscore the importance of accurately determining the volcanic plume height when deriving SO2 emissions from satellite data.

Mineral dust particles significantly influence the Earth’s climate through direct and semi-direct radiative effects. This study investigates these effects and their meteorological impacts during a dust intrusion and heatwave over the Iberian Peninsula in summer 2019 using a regional climate model. Three simulations with different spectral nudging configurations are evaluated. During the central period, the mean direct and semi-direct radiative effects in the shortwave spectrum at the top of the atmosphere (bottom of the atmosphere) are −0.4 ± 0.4 (−3.9 ± 2.3) Wm−2 and +0.1 ± 1.7 (−0.1 ± 1.9) Wm−2, respectively. In the longwave spectrum, these effects are +0.1 ± 0.1 (+0.3 ± 0.1) Wm−2 and 0.0 ± 0.6 (+0.9 ± 1.1) Wm−2, respectively. The semi-direct effect mitigates 18.8% of the dust-induced warming in the full atmosphere and alters meteorological variables. The liquid water path decreases by −0.2 ± 4.5 mg m−2, the cloud fraction in the upper (lower) troposphere reduces (increases) by −0.2 ± 1.2 (+0.1 ± 1.3) %, and the near-surface air temperature drops slightly by −0.2 ± 0.2 ∘C. The results highlight substantial spatial variability and underscore the importance of considering semi-direct radiative effects in radiative analysis.

The Raman lidar technique to measure atmospheric temperature profiles is based on the dependence on temperature of the intensity of the atmospheric N2 and O2 rotational Raman lines [1]. The technique requires very good stability of the laser wavelength, or frequent recalibrations, to avoid errors in the retrieved temperature produced by wavelength drifts. Frequency doubled or tripled Nd:YAG lasers are usually employed to implement this technique. To achieve laser wavelength stability, injection-seeded lasers are used that transfer the wavelength stability of the seeder to the high-power laser [2]; this has also the consequence of narrowing the spectrum of the transmitted radiation. Temperature profiling using free-running lasers are also reported in the literature [3]. In this case wavelength stability must be obtained by keeping the laser operating conditions, and in particular the Nd:YAG rod temperature, very stable.We have assessed the effects on the atmospheric temperature retrieval of the spectral width and temperature-induced wavelength drift of the 3rd harmonic of a free-running Nd:YAG laser. We have found that the spectral width has a negligible effect, as compared with the negligible spectral width of an injection-seeded laser, in the receiving filters that are part of the lidar. However, slight temperature-induced drifts on the central wavelength of the laser emitted spectrum entail small changes in the filter responses that impair the calibration and cause an uncertainty in the retrieved atmosphere temperature. We have estimated that to keep the retrieved temperature uncertainty below 1 K, the rod temperature must also to be kept within a ±1 K range. This is also the temperature stability that would be needed in the seeder of an injection seeded laser, as changes of temperature in the seeder will also cause wavelength drifts, hence uncontrolled biases in the atmosphere temperature measurements that would add to their uncertainty. [1] J. Cooney, Measurement of Atmospheric Temperature Profiles by Raman Backscatter, J Appl Meteorol Climatol. 11 (1972) 108–112. https://doi.org/10.1175/1520-0450(1972)0112.0.CO;2[2] E. Hammann, A. Behrendt, F. Le Mounier, V. Wulfmeyer, Temperature profiling of the atmospheric boundary layer with rotational Raman lidar during the HD(CP)2 Observational Prototype Experiment, Atmos Chem Phys. 15 (2015) 2867–2881. https://doi.org/10.5194/acp-15-2867-2015.[3] P. Di Girolamo, R. Marchese, D.N. Whiteman, B.B. Demoz, Rotational Raman Lidar measurements of atmospheric temperature in the UV, Geophys Res Lett. 31 (2004) 1–5. https://doi.org/10.1029/2003GL018342.

This study attempts to quantify the radiative impact over R & eacute;union Island (21 degrees S, 55 degrees E) in the southern tropical Indian Ocean of the aerosols and water vapor (WV) injected into the stratosphere by the eruption of the Hunga underwater volcano in the South Pacific on 15 January 2022 . Ground-based lidar and satellite passive instruments are used to parameterize a state-of-the-art radiative transfer (RT) model for the first 13 months after the volcano eruption. The descending rate of the aerosol volcanic plume is -8 m d-1. At this rate, aerosols are expected to be present in the stratosphere until the first half of 2025. The overall aerosol and water vapor impact on the Earth's radiation budget for the whole period is negative (cooling, -0.82 +/- 0.35 W m-2) and dominated by the aerosol impact (similar to 95 %; the remaining similar to 5 % is due to the water vapor). At the Earth's surface, aerosols are the main drivers and produce a negative (cooling, -1.04 +/- 0.36 W m-2) radiative impact. Water vapor has hardly any radiative effect at the surface. Between the short-term (months 2 to 4 after the eruption, February-April 2022) and mid-term (months 5 to 14 after the eruption, May 2022-February 2023) periods, the aerosol and water vapor radiative effect at the surface and top of atmosphere (TOA) reduces by 22 % and 25 %, respectively. During the mid-term period, heating / cooling (H / C) rate profiles show a clear vertical difference locally in the stratosphere between the aerosol warming impact (18 to 26 km) and the water vapor cooling (22 to 30 km). The resulting aerosol and water vapor heating / cooling rate profile follows an S-shaped curve with peaks slightly larger for the moist layer (-0.09 K d-1) than for the sulfate layer (+0.06 K d-1).

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.

On 15 January 2022, the Hunga volcano (20.5 degrees S, 175.4 degrees E) erupted, releasing significant amounts of water vapor (H2O) and a moderate quantity of sulfur dioxide into the stratosphere. The resulting volcanic plume traveled westward with the southern hemispheric stratospheric circulation, reaching the Indian Ocean and R & eacute;union (21.1 degrees S, 55.5 degrees E) within days. This study presents the first analysis of Infrared Atmospheric Sounding Interferometer (IASI) ozone data to investigate the impact of the Hunga eruption, and also incorporates Microwave Limb Sounder (MLS) and Ozone Mapping and Profiler Suite Limb Profiler (OMPS-LP) data, as well as ground-based measurements from R & eacute;union. IASI observations revealed a transient ozone depletion event in the first week following the eruption. OMPS-LP aerosol extinction profiles, sun-photometer measurements, and lidar observations characterized the plume's vertical and latitudinal extent, showing its presence over R & eacute;union at altitudes ranging from 26.8 to 29.7 km and its spread across more than 30 degrees longitude and 20 degrees latitude by 21 January. IASI ozone spatial distributions showed marked decreases in total and stratospheric ozone on that date, with the fifth percentile of the anomaly reaching -18.6 DU for total column ozone and -14.5 DU for stratospheric column ozone. A key finding, as shown by MLS profiles, is that the ozone reduction was confined to two separate layers (-0.7 +/-(1 sigma) 0.6 ppmv in the 14.68-12.12 hPa range, and -0.6 +/-(1 sigma) 0.5 ppmv in the 31.62-21.54 hPa range), each associated with a distinct aerosol cloud with excess H2O. This layered structure of ozone loss offers new insight into the chemical and radiative effects of the Hunga plume on stratospheric ozone.