We use the CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) instrument to determine the microphysical properties of the stratospheric aerosol plume after the Hunga eruption in 2022, the largest so far after the Pinatubo in 1991. In the early stages, low depolarization (<2%) is found everywhere except in patches of high depolarization (up to 35 %) detected within the plumes of sulfur compounds up to 3 d after the eruption. As standard CALIOP L2 products are not operational in the case of the Hunga aerosol plume, we implement an iterative method of successive approximations to retrieve extinction profiles, by estimating the aerosol optical depth (AOD) and then the lidar ratio (LR). The AOD of the plume at 532 nm is between 0.5 and 1.25 on the first four days, then decreases rapidly and stabilizes at 0.047 +/- 0.011 for March 2022. The LR is initially between 60 and 80 sr, consistent with the early growth of sulfate aerosol particles, and then decreases to 48 +/- 6sr between late January and late March 2022. Results are compared and validated with the solar occultation instrument SAGE III (Stratospheric Aerosol and Gas Experiment) on board the International Space Station (ISS) and Mie calculations. A comparison with limb-viewing instruments highlights significant quantitative disagreements in extinction and AOD estimates, which we attribute, in part, to the unusual size distribution of the aerosols within the Hunga plume.

Following the eruptions of Raikoke in 2019 and Hunga in 2022, it was recently discovered that stratospheric volcanic plumes may feature specific mesoscale dynamics. First, they undergo important vertical motions, a descent for the Hunga plume [e.g., 1,2], a self-lofting for the Raikoke plume [e.g., 3]. Second, they tend to self-organize into mesoscale anticyclonic circulations. This behavior dramatically affects the dispersion of the plumes and their climate impacts. While it is clear that they arise due to significant diabatic heating anomalies, a quantitative estimate of the radiative heating rates and their link with the vertical motions of the plumes is currently lacking .In this study, we use offline radiative transfer calculations with a broad-band radiative transfer model to quantify the anomalous stratospheric heating rates resulting from a localized volcano-induced perturbation. The calculations are forced using particle optical properties and water vapor concentrations in the Hunga and Raikoke plumes observed from a suite of space-borne sensors including the spaceborne Lidar CALIOP. We explore the sensitivity of the heating rates to various plume properties, including altitude and composition. Their consequences on mesoscale organization are discussed in light of idealized mesoscale plume simulations [4]. References[1] Sellitto, P., Podglajen, A., Belhadji, R. et al. The unexpected radiative impact of the Hunga Tonga eruption of 15th January 2022. Commun Earth Environ 3, 288 (2022). https://doi.org/10.1038/s43247-022-00618-z[2] Legras, B., Duchamp, C., Sellitto, P., Podglajen, A., Carboni, E., Siddans, R., Grooß, J.-U., Khaykin, S., and Ploeger, F.: The evolution and dynamics of the Hunga Tonga–Hunga Ha'apai sulfate aerosol plume in the stratosphere, Atmos. Chem. Phys., 22, 14957–14970, https://doi.org/10.5194/acp-22-14957-2022, 2022.[3] Khaykin, S.M., de Laat, A.T.J., Godin-Beekmann, S. et al. Unexpected self-lofting and dynamical confinement of volcanic plumes: the Raikoke 2019 case. Sci Rep 12, 22409 (2022). https://doi.org/10.1038/s41598-022-27021-0[4] Podglajen, A., Legras, B., Lapeyre, G., Plougonven, R., Zeitlin, V., Brémaud, V., et al. (2024) Dynamics of diabatically forced anticyclonic plumes in the stratosphere. Quarterly Journal of the Royal Meteorological Society, 150(760), 1538–1565. https://doi.org/10.1002/qj.4658

The increasing severity and duration of forest fire seasons, exemplified by the Canadian fires of 2017 (Pacific Northwest Event) and the Australian fires of 2019-2020 (Australian New Year's event), have highlighted the significant impact of these events on the stratosphere. Through intense pyrocumulonimbus activity, these fires injected large quantities of gases, biomass burning products, and other pollutants into the stratosphere. During both fires, a unique phenomenon was observed, i.e. the formation of vortex structures in the stratosphere.Theses vortex structures confined the injected mixture of gases and aerosols, transporting them over weeks in the case of the Canadian fires and months for the Australian fires. These vortices caused localized disturbances in stratospheric chemical composition and triggered specific chemical reactions.This study focuses on the localized impact created by these vortices, particularly their role in ozone depletion. By confining and transporting biomass combustion products, these vortex structures created conditions for unique chemistry. Data from the Microwave Limb Sounder (MLS) and the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) revealed substantial increases in water vapor and biomass burning tracers, including CO, CH₃Cl, HCN, and CH₃OH. Simultaneously, significant depletions were observed in critical stratospheric reservoirs such as HNO₃, ClONO₂, and HCl. This was accompanied by a marked decrease in ozone mixing ratios with respect to unperturbed conditions, initially associated with injection of ozone-poor tropospheric air but maintained throughout the course of the vortices, questioning about the occurrence of potential ozone destruction through heterogeneous chemical processes, even if no direct evidence of chlorine activation is observed.Similarities in the chemical content are clearly highlighted for these two events. While this analysis sheds light on the impact of these vortices on stratospheric chemistry, further investigations are necessary to explore the role of organic compounds in the observed ozone depletion and to better understand the broader implications of increasingly severe wildfire events on atmospheric composition and dynamics.

The Hunga Tonga-Hunga Ha'apai volcano violently erupted on 15 January 2022 and produced the largest stratospheric aerosol layer perturbation of the last 30 years. In comparison to background conditions and other recent moderate stratospheric eruptions, one notable effect of the Hunga Tonga-Hunga Ha'apai eruption was the significant modification of the size distribution (SD) of the stratospheric aerosol layer, resulting in a larger mean particle size and a smaller SD spread for Hunga Tonga-Hunga Ha'apai. Starting from satellite-based SD retrievals and the assumption of pure sulfate aerosol layers, in this work, we calculate the optical properties of both background and Hunga Tonga-Hunga Ha'apai-perturbed stratospheric aerosol scenarios using a Mie code. We found that the intensive optical properties of the stratospheric aerosol layer (i.e. the single-scattering albedo (SSA), the asymmetry parameter, the aerosol extinction per unit mass, and the broad-band average ultraviolet-visible (UV-Vis) to mid-infrared (MIR) & Aring;ngstr & ouml;m exponent (AE)) were not significantly perturbed by the Hunga Tonga-Hunga Ha'apai eruption with respect to background conditions. The calculated AE was found to be consistent with multi-instrument satellite observations of the same parameter. Thus, the basic impact of the Hunga Tonga-Hunga Ha'apai eruption on the optical properties of the stratospheric aerosol layer was an increase in the stratospheric aerosol extinction (or optical depth), without any modification of the shortwave (SW) and longwave (LW) relative absorption, angular scattering, and broad-band spectral trend of the extinction, with respect to background. This highlights a marked difference between the Hunga Tonga-Hunga Ha'apai perturbation of the stratospheric aerosol layer and perturbations from other larger stratospheric eruptions, such as Pinatubo 1991 and El Chich & oacute;n 1982. With simplified radiative forcing estimations, we show that the Hunga Tonga-Hunga Ha'apai eruption produced an aerosol layer likely 1.5-10 times more effective in producing a net cooling of the climate system with respect to the Pinatubo and El Chich & oacute;n eruptions due to more effective SW scattering. As intensive optical properties are seldom directly measured, e.g. from satellite, our calculations can support the estimation of radiative effects for the Hunga Tonga-Hunga Ha'apai eruption with climate or offline radiative models.

Abstract. The Hunga volcano violently erupted on January 15th, 2022, and produced the largest stratospheric aerosol layer perturbation of the last 30 years. One notable effect of the Hunga eruption was the significant modification of the size distribution (SD) of the stratospheric aerosol layer with respect to background conditions and other recent moderate stratospheric eruptions, with larger mean particles size and smaller SD spread for Hunga. Starting from satellite-based SD retrievals, and the assumption of pure sulphate aerosol layers, in this work we calculate the optical properties of both background and Hunga-perturbed stratospheric aerosol scenarios using a Mie code. We found that the intensive optical properties of the stratospheric aerosol layer (i.e., single scattering albedo, asymmetry parameter, aerosol extinction per unit mass and the broad-band average Ångström exponent) were not significantly perturbed by the Hunga eruption, with respect to background conditions. The calculated Ångström exponent was found consistent with multi-instrument satellite observations of the same parameter. Thus, the basic impact of the Hunga eruption on the optical properties of the stratospheric aerosol layer was an increase of the stratospheric aerosol extinction (or optical depth), without any modification of the shortwave and longwave relative absorption, angular scattering and broad-band spectral trend of the extinction, with respect to background. This highlights a marked difference of the Hunga perturbation of the stratospheric aerosol layer and those from other larger stratospheric eruptions, like Pinatubo 1991 and El Chichon 1982. With simplified radiative forcing estimations, we show that the Hunga eruption produced an aerosol layer likely 3–10 times more effective in producing a net cooling of the climate system with respect to Pinatubo and El Chichon eruptions, due to more effective shortwave scattering. As intensive optical properties are seldom directly measured, e.g. from satellite, our calculations can support the estimation of radiative effects for the Hunga eruption with climate or offline radiative models.

AbstractThe Hunga volcano violently erupted on 15 January 2022, producing the largest perturbation of the stratospheric aerosol layer since Pinatubo 1991, despite the initially estimated modest injection of SO2. This study presents novel SO2 and sulfate aerosol (SA) co‐retrievals from the Infrared Atmospheric Sounding Interferometer, and uses them to quantify the initial progression of the Hunga plume. These observations are consistent with rapid conversion of SO2 (e‐folding time: 17.1 ± 4.3 days) to SA, with an injected burden of >1.0 Tg SO2. This points at larger SO2 injections than previously thought. A long‐lasting SA plume was observed, with two separate build‐up phases, and with a meridional dispersion of marked anomalies from the tropics to the higher southern hemispheric latitudes. A limited (∼20%) SA removal was observed after 1‐year dispersion. The total injected SA mass burden was estimated at 1.6 ± 0.5 Tg in the total atmospheric column, with a build‐up e‐folding time of about 2 months.

The underwater Hunga Tonga-Hunga Ha’apai (HTHH) volcano erupted in the early hours of 15th January 2022 and injected volcanic gases and aerosols to over 50 km altitude. This eruption produced the largest global perturbation of stratospheric aerosols since the Pinatubo eruption in 1991 and the largest perturbation of stratospheric water vapour observed in the satellite era. Using offline radiative transfer modelling and observations, it was shown that the combined radiative effect of the water vapour and aerosol perturbations from the HTHH eruption produced a positive radiative forcing at TOA (top-of-atmosphere), leading to a net warming of the climate system, and a fast radiatively-driven plume descent, during the first month after the event (Sellitto et al., 2022). This was the first time a warming effect on the climate system and a plume sinking was linked to volcanic eruptions, which usually produce a transient cooling and a possible plume lofting. Building on these first analyses, we synthesise satellite, ground-based, in situ and radiosonde observations accumulated after 2 years since the eruption and we investigate the evolution of the radiative impacts at this temporal scale. As aerosols sedimented and the water vapour was entrained in the ascending branch Brewer–Dobson circulation, a clear vertical separation of the stratospheric aerosol and the moisture anomaly were observed; the effect of this vertical separation on the TOA radiative forcing and localised atmospheric diabatic heating/cooling is analysed and discussed. Reference:Sellitto, P., Podglajen, A., Belhadji, R. et al. The unexpected radiative impact of the Hunga Tonga eruption of 15th January 2022. Commun Earth Environ 3, 288 (2022). https://doi.org/10.1038/s43247-022-00618-z

The volcanic cloud generated by the 15 January 2022 eruption of the Hunga Tonga-Hunga Ha'apai (HTHH) volcano reached unprecedented altitudes in the modern observational record, with a maximum reported height of approximately 57 km, and an umbrella cloud at around 35 km. Over the first two weeks following the eruption, the stratospheric sulfate aerosol plume underwent a rapid descent, which was attributed to radiative cooling induced by a substantial water vapor anomaly [1, 2]. However, a comprehensive understanding of the initial subsidence of the plume—from its injection at about 35 km to its subsequent observation over La Reunion a few days later at around 29-30 km—is currently lacking. In this study, we use offline radiative transfer calculations to quantify the anomalous stratospheric heating rates resulting from a localized volcano-induced perturbation. We explore their sensitivity to various plume properties, including altitude and composition (e.g. in water vapor, ozone, and sulfate aerosols). Then, these radiative calculations are combined with Lagrangian trajectories using the ERA5 reanalysis model to reconstruct the early dispersion of the HTHH plume. The results are compared with the 3D plume structure inferred from satellite data (CALIOP, geostationary, GPS-radiooccultations, IASI-IMS) and Australian radiosonde observations. References [1] Sellitto, P., Podglajen, A., Belhadji, R. et al. The unexpected radiative impact of the Hunga Tonga eruption of 15th January 2022. Commun Earth Environ 3, 288 (2022). https://doi.org/10.1038/s43247-022-00618-z [2] Legras, B., Duchamp, C., Sellitto, P., Podglajen, A., Carboni, E., Siddans, R., Grooß, J.-U., Khaykin, S., and Ploeger, F.: The evolution and dynamics of the Hunga Tonga–Hunga Ha'apai sulfate aerosol plume in the stratosphere, Atmos. Chem. Phys., 22, 14957–14970, https://doi.org/10.5194/acp-22-14957-2022, 2022. [3] Baron, A., Chazette, P., Khaykin, S., Payen, G., Marquestaut, N., Bègue, N., & Duflot, V. (2023). Early evolution of the stratospheric aerosol plume following the 2022 Hunga Tonga-Hunga Ha'apai eruption: Lidar observations from Reunion (21°S, 55°E). Geophysical Research Letters, 50, e2022GL101751. https://doi-org.insu.bib.cnrs.fr/10.1029/2022GL10175

Abstract The Tonga eruption of 15 January 2022 has released a long‐lived stratospheric plume of sulfate aerosols. More than 17 months after, we focus on the high quality data series of SAGE III (Stratospheric Aerosol and Gas Experiment) on board the International Space Station (ISS) to determine the mean radius and size distribution of the aerosols and their total mass. The persisting volcanic aerosols—with a mode width of 1.25 and an effective radius of 0.4 μm—differ from the significantly smaller background aerosols and from those measured during recent stratospheric eruptions. The sulfuric acid mass between 50°S and 30°N is estimated to be very stable in spite of considerable redistribution in latitude at a value of 0.66 ± 0.1 Tg, corresponding to an initial sulfur dioxide emission of 0.44 Tg. Such properties are expected to facilitate the persistence of a climate warming due to the volcanic water vapor.

The Hunga Tonga-Hunga Ha’apai volcano violently erupted on 15 January 2022, producing the largest perturbation of the stratospheric aerosol layer since Pinatubo 1991, despite the estimated modest injection of SO2. Here we present novel SO2 and sulphate aerosol (SA) co-retrievals from the Infrared Atmospheric Sounding Instrument, and use them to study the dispersion of the Hunga Tonga plume over the entire year 2022. We observe rapid conversion of SO2 (e-folding time: 17.1±0.6 days) to sulphate aerosols (SA), with an initial injected burden of >1.0 Tg. This points at larger SO2 injections than previously thought. A long-lasting SA plume was observed, with a meridional dispersion of marked anomalies from the tropics to the higher southern hemispheric latitudes. A very small SA removal is observed after 1-year dispersion. The total SA mass burden was estimated at 1.6 ± 0.1 Tg in total column, with a build-up e-folding time of about 2 months.

We use a combination of seven space-borne instruments to study the unprecedented stratospheric plume after the Tonga eruption of 15 January 2022.The aerosol plume was initially formed of two clouds at 30 and 28 km mostly composed of submicron-sized sulfate particles, without ashes washed-out within the first day following the eruption. The large amount of injected water vapour led to a fast conversion of SO2 to sulfate aerosols and induced a descent of the plume to 24-26 km over the first 3 weeks by radiative cooling. Whereas SO2 has returned to background levels by the end of January, volcanic sulfates and water still persisted after 6 months, mainly confined between 35°S and 20°N until June due to the zonal symmetry of the summer stratospheric circulation at 22-26 km. Sulfate particles, undergoing hygroscopic growth and coagulation, sediment and gradually separate from the moisture anomaly entrained in the ascending branch Brewer-Dobson circulation. Sulfate aerosol optical depths derived from the IASI infrared sounder show that during the first two months the aerosol plume was not simply diluted and dispersed passively but rather organized in concentrated patches. Space-borne lidar winds suggest that those structures, generated by shear-induced instabilities, were associated with vorticity anomalies that may have enhanced the duration and impact of the plume.Reference: ACP Highlight, DOI: 10.5194/acp-22-14957-2022

&lt;p&gt;The underwater Hunga Tonga-Hunga Ha&amp;#8217;apai volcano erupted in the early hours of 15th January 2022 and injected volcanic gases and aerosols to over 50&amp;#8201;km altitude. In this talk, we synthesise satellite, ground-based, in situ and radiosonde observations of the eruption to investigate the emissions, the horizontal and vertical dispersion, and the strength of the stratospheric aerosol and water vapour perturbations in the initial six months after the eruption. The aerosol plume was initially formed of two clouds at 30 and 28 &amp;#8201;km, mostly composed of submicron-sized sulfate particles, without ash, which is washed out within the first day following the eruption. The large amount of injected water vapour led to a fast conversion of SO2 to sulphate aerosols. We find that the Hunga Tonga-Hunga Ha&amp;#8217;apai eruption produced the largest global perturbation of stratospheric aerosols since the Pinatubo eruption in 1991 and the largest perturbation of stratospheric water vapour observed in the satellite era. Then, using offline radiative transfer calculations driven by aerosol and water vapour observations, we quantify the net radiative impact across the two species. Immediately after the eruption, water vapour radiative cooling dominated the local stratospheric heating/cooling rates, producing a spectacular radiatively-driven plume descent of several kilometres. At the top-of-the-atmosphere and surface, volcanic aerosol cooling dominated the radiative forcing during this first dispersion phase. However, after two weeks, due to dilution, water vapour heating started to dominate the top-of-the-atmosphere radiative forcing, leading to a net warming of the climate system. On a longer timescale, sulphate particles, undergoing hygroscopic growth and coagulation, sediment and gradually separate from the moisture anomaly entrained in the ascending branch Brewer&amp;#8211;Dobson circulation. This is the first time a warming effect on the climate system has been linked to volcanic eruptions, which usually produce a transient cooling.&lt;/p&gt;

&lt;p&gt;Recent extreme events associated with forest fires and large volcanic eruptions have demonstrated that dense aerosol clouds in the stratosphere often wraps up as persistent compact structures which rotate as anticyclones and also move vertically. One of these vortices has been observed over 3 months and experienced a 20 km rise. Such observations were made after the 2020 Australian wildfires, the 2017 British Columbia fire and more recently after the 2022 Tonga eruption and a few other cases. For all these events, the link was made with anomalous warming or cooling due to the composition of the clouds. This presentation will summarize the observed events and demonstrate the general characters of the stratospheric aerosol vortices. It will also discuss how they are detected by the weather assimilation systems through their signature in temperature, the conditions of their stability and how they can be reproduced experimentally with simple experimental models. Their impact on the transport of long-lived species will be discussed.&lt;/p&gt; &lt;p&gt;Such structures seem so far proper to the Earth stratosphere and have found analogies nowhere else.&lt;/p&gt; &lt;p&gt;Ref: DOIs: 10.1038/s43247-020-00022-5, 10.5194/acp-21-7113-2021, 10.5194/acp-22-14957-2022&lt;/p&gt;

Following the Hunga Tonga eruption (20.6°S, 175.4°W, mid‐January 2022), we present a balloon‐borne characterization of the stratospheric aerosol plume one week after its injection (on 23 and 26 January 2022, La Réunion island at 21.1°S, 55.3°E). Satellite observations show that flight (a) took place during the overpass of a denser plume of sulfate aerosols (SA) compared to a more diluted plume during flight. (b) Observations show that the sampled plumes (at around 22, 25 and 19 km altitude, respectively) consist exclusively of very small particles (with radius <1 µm). Particles with radii between 0.5 and 1.0 µm show optically transparent features pointing to predominant SA. Particles with radii below 0.5 µm are partly absorbing, which could point to small sulfate coated ash particles, a feature not identified with space‐borne observations. This shows that in situ observations are necessary to fully characterize the microphysical properties of the plumes tracked by space‐borne instruments.

The underwater Hunga Tonga-Hunga Ha-apai volcano erupted in the early hours of 15th January 2022, and injected volcanic gases and aerosols to over 50 km altitude. Here we synthesise satellite, ground-based, in situ and radiosonde observations of the eruption to investigate the strength of the stratospheric aerosol and water vapour perturbations in the initial weeks after the eruption and we quantify the net radiative impact across the two species using offline radiative transfer modelling. We find that the Hunga Tonga-Hunga Ha-apai eruption produced the largest global perturbation of stratospheric aerosols since the Pinatubo eruption in 1991 and the largest perturbation of stratospheric water vapour observed in the satellite era. Immediately after the eruption, water vapour radiative cooling dominated the local stratospheric heating/cooling rates, while at the top-of-the-atmosphere and surface, volcanic aerosol cooling dominated the radiative forcing. However, after two weeks, due to dispersion/dilution, water vapour heating started to dominate the top-of-the-atmosphere radiative forcing, leading to a net warming of the climate system.

We use a combination of spaceborne instruments to study the unprecedented stratospheric plume after the Tonga eruption of 15 January 2022. The aerosol plume was initially formed of two clouds at 30 and 28 km, mostly composed of submicron-sized sulfate particles, without ash, which is washed out within the first day following the eruption. The large amount of injected water vapour led to a fast conversion of SO2 to sulfate aerosols and induced a descent of the plume to 24–26 km over the first 3 weeks by radiative cooling. Whereas SO2 returned to background levels by the end of January, volcanic sulfates and water still persisted after 6 months, mainly confined between 35∘ S and 20∘ N until June due to the zonal symmetry of the summer stratospheric circulation at 22–26 km. Sulfate particles, undergoing hygroscopic growth and coagulation, sediment and gradually separate from the moisture anomaly entrained in the ascending branch Brewer–Dobson circulation. Sulfate aerosol optical depths derived from the IASI (Infrared Atmospheric Sounding Interferometer) infrared sounder show that during the first 2 months, the aerosol plume was not simply diluted and dispersed passively but rather organized in concentrated patches. Space-borne lidar winds suggest that those structures, generated by shear-induced instabilities, are associated with vorticity anomalies that may have enhanced the duration and impact of the plume.

Les éruptions volcaniques majeures et les mégafeux de forêt peuvent injecter d'importantes quantités de gaz, d'aérosols et de vapeur d'eau dans la stratosphère, modifiant sa composition et sa dynamique, et perturbant potentiellement le bilan radiatif local et global. Cette thèse, fondée sur l'analyse d'observations satellitaires multi-instrumentales, vise à caractériser les panaches stratosphériques issus de deux événements récents exceptionnels : l'éruption du Hunga (2022) et les mégafeux australiens (2019-2020).L'éruption du Hunga du 15 janvier 2022, d'une explosivité extrême (indice d'explosivité volcanique proche de 6), a battu plusieurs records de l'ère satellitaire, avec une altitude maximale du panache atteignant environ 58 km et une injection exceptionnelle de vapeur d'eau estimée à 150 Tg dans la stratosphère habituellement sèche (soit près de 10 % de son contenu global). L'analyse combinée de plusieurs instruments a permis de retracer les phases de conversion rapide du SO2 en aérosols sulfatés accélérée par la forte humidité, ainsi que l'évolution d'abord conjointe, puis séparée, des panaches d'aérosols et de vapeur d'eau dans la stratosphère. Les propriétés microphysiques des aérosols (rayon effectif ~ 0.4 µm, déviation standard géométrique ~ 1.25), différentes des conditions de fond et d'autres éruptions stratosphériques récentes, ont été restituées à partir des mesures spectrales de SAGE III/ISS, permettant une estimation précise de la masse d'aérosols sulfatés (0.66 ± 0.1 Tg H2SO4). Les propriétés optiques (extinction et rapport lidar) dérivées des mesures CALIOP montrent une excellente cohérence avec les calculs de Mie et les observations de SAGE III/ISS, tout en soulignant les limites des produits d'extinction au limbe dans le cas de distributions d'aérosols atypiques. Les mégafeux australiens de décembre 2019-janvier 2020 ont quant à eux démontré la capacité des pyrocumulonimbus à injecter des masses considérables de fumées dans la stratosphère, engendrant la formation de vortex stratosphériques anticycloniques. Le vortex principal a présenté une auto-élévation remarquable de 15 à 36 km sur trois mois. Nous montrons que les zones de forte vorticité coïncident avec les régions de confinement maximal des aérosols de fumée. L'analyse des rapports de mélange met en évidence un appauvrissement en ozone, une vapeur d'eau stable mais élevée, et une diminution progressive des traceurs de combustion, suggérant une évolution chimique propre au vortex et un faible impact de la dilution ou du mélange avec les masses d'air environnantes. L'ensemble des travaux présentés contribue à améliorer la compréhension des processus physico-chimiques qui régissent l'évolution des panaches stratosphériques issus d'événements extrêmes. Ils soulignent également les défis persistants liés à la caractérisation des aérosols non sphériques et à la variabilité croissante du fond stratosphérique, dans un contexte de multiplication des événements extrêmes et de réchauffement global.