Articles | Volume 25, issue 12
https://doi.org/10.5194/acp-25-6353-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/acp-25-6353-2025
© Author(s) 2025. This work is distributed under
the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
The optical properties of the stratospheric aerosol layer perturbation of the Hunga Tonga–Hunga Ha'apai volcano eruption of 15 January 2022
Pasquale Sellitto
CORRESPONDING AUTHOR
Univ Paris Est Creteil and Université de Paris, CNRS, LISA, 94010 Créteil, France
Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo, Catania, Italy
Redha Belhadji
Univ Paris Est Creteil and Université de Paris, CNRS, LISA, 94010 Créteil, France
Bernard Legras
Laboratoire de Météorologie Dynamique (LMD-IPSL), CNRS, Sorbonne Université, ENS-PSL, École Polytechnique, Paris, France
Aurélien Podglajen
Laboratoire de Météorologie Dynamique (LMD-IPSL), CNRS, Sorbonne Université, ENS-PSL, École Polytechnique, Paris, France
Clair Duchamp
Laboratoire de Météorologie Dynamique (LMD-IPSL), CNRS, Sorbonne Université, ENS-PSL, École Polytechnique, Paris, France
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Spectroscopy measurements show that the absorbance of dust in the far-infrared up to 25 μm is comparable in intensity to that in the mid-infrared (3–15μm) suggesting its relevance for dust direct radiative effect. Data evidence different absorption signatures for high and low/mid latitude dust, due to differences in mineralogical composition. These differences could be used to characterise the mineralogy and differentiate the origin of airborne dust based on infrared remote sensing observations.
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Record-breaking wildfires ravaged south-eastern Australia during the fire season 2019–2020. These fires injected a smoke plume in the stratosphere, which dispersed over the whole Southern Hemisphere and interacted with solar and terrestrial radiation. A number of detached smoke bubbles were also observed emanating from this plume and ascending quickly to over 35 km altitude. Here we study how absorption of radiation generated ascending motion of both the the hemispheric plume and the vortices.
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Claudia Di Biagio, Elisa Bru, Avila Orta, Servanne Chevaillier, Clarissa Baldo, Antonin Bergé, Mathieu Cazaunau, Sandra Lafon, Sophie Nowak, Edouard Pangui, Meinrat O. Andreae, Pavla Dagsson-Waldhauserova, Kebonyethata Dintwe, Konrad Kandler, James S. King, Amelie Chaput, Gregory S. Okin, Stuart Piketh, Thuraya Saeed, David Seibert, Zongbo Shi, Earle Williams, Pasquale Sellitto, and Paola Formenti
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Spectroscopy measurements show that the absorbance of dust in the far-infrared up to 25 μm is comparable in intensity to that in the mid-infrared (3–15μm) suggesting its relevance for dust direct radiative effect. Data evidence different absorption signatures for high and low/mid latitude dust, due to differences in mineralogical composition. These differences could be used to characterise the mineralogy and differentiate the origin of airborne dust based on infrared remote sensing observations.
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In October 2022, we detected volcanic particles in the stratosphere over France, linked to the January 2022 Hunga eruption in the South Pacific. Found between 17 and 23 km altitude, they were traced back to the tropics using trajectory simulations and satellite data. Their optical properties matched those in the Southern Hemisphere. The particles spread across the Northern Hemisphere, reflecting sunlight and slightly cooling the surface—a small but non-negligible effect.
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Short summary
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We analyzed the stratospheric aerosol plume from the 2022 Hunga eruption using satellite lidar data. We implemented a method to retrieve some aerosol properties, as standard products failed in this case. We found very high optical depth values in the days following the eruption, which decreased rapidly but remained elevated for months. Our results are broadly validated, though some satellite products underestimate the values due, in part, to the unusual aerosol size distribution in the plume.
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The 2019–2020 Australian wildfires triggered massive Pyro-cumulonimbus clouds, injecting smoke aerosols into the stratosphere and forming a self-sustaining vortex that reached 35 km altitude. This vortex created a transient ozone mini-hole. Using satellite and ground-based observations, we tracked a 30–40 % initial ozone depletion, which decayed to ~7 % within a month. These findings highlight the impact of extreme wildfires on stratospheric dynamics and ozone composition.
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Pasquale Sellitto, Audrey Gaudel, and Bastien Sauvage
EGUsphere, https://doi.org/10.5194/egusphere-2024-3748, https://doi.org/10.5194/egusphere-2024-3748, 2025
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Tropospheric ozone is a potent greenhouse gas; its anthropogenic levels rise contributes to climate change. We evaluate tropospheric ozone trends and climate impacts with aircraft data and a radiative model, comparing the baseline period (1994–2004) to 2011–2016 and 2019. Tropospheric ozone levels increased significantly but with a smaller trend in 2019 than in 2011–2016. However, ozone radiative forcing did not decrease between these periods because of different vertical distribution evolutions
Michaël Sicard, Alexandre Baron, Marion Ranaivombola, Dominique Gantois, Tristan Millet, Pasquale Sellitto, Nelson Bègue, Hassan Bencherif, Guillaume Payen, Nicolas Marquestaut, and Valentin Duflot
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Thomas Lesigne, François Ravetta, Aurélien Podglajen, Vincent Mariage, and Jacques Pelon
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Pasquale Sellitto, Redha Belhadji, Juan Cuesta, Aurélien Podglajen, and Bernard Legras
Atmos. Chem. Phys., 23, 15523–15535, https://doi.org/10.5194/acp-23-15523-2023, https://doi.org/10.5194/acp-23-15523-2023, 2023
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The role of gravity waves on tropical cirrus clouds and air-parcel dehydration was studied using the combination of Lagrangian observations of temperature fluctuations from superpressure balloons and a 1.5D model. The inclusion of the gravity waves to a reference simulation of a slow ascent around the cold-point tropopause drastically increases ice-crystal density, cloud fraction, and air-parcel dehydration, and it produces a crystal size distribution that agrees better with observations.
Richard Wilson, Clara Pitois, Aurélien Podglajen, Albert Hertzog, Milena Corcos, and Riwal Plougonven
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Mathieu Lachatre, Sylvain Mailler, Laurent Menut, Arineh Cholakian, Pasquale Sellitto, Guillaume Siour, Henda Guermazi, Giuseppe Salerno, and Salvatore Giammanco
Atmos. Chem. Phys., 22, 13861–13879, https://doi.org/10.5194/acp-22-13861-2022, https://doi.org/10.5194/acp-22-13861-2022, 2022
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Short summary
In this study, we have evaluated the predominance of various pathways of volcanic SO2 conversion to sulfates in the upper troposphere. We show that the main conversion pathway was gaseous oxidation by OH, although the liquid pathways were expected to be predominant. These results are interesting with respect to a better understanding of sulfate formation in the middle and upper troposphere and are an important component to help evaluate particulate matter radiative forcing.
Pasquale Sellitto, Redha Belhadji, Corinna Kloss, and Bernard Legras
Atmos. Chem. Phys., 22, 9299–9311, https://doi.org/10.5194/acp-22-9299-2022, https://doi.org/10.5194/acp-22-9299-2022, 2022
Short summary
Short summary
As a consequence of extreme heat and drought, record-breaking wildfires ravaged south-eastern Australia during the fire season in 2019–2020. Fires injected a smoke plume very high up to the stratosphere, which dispersed quite quickly to the whole Southern Hemisphere and interacted with solar radiation, reflecting and absorbing part of it – thus producing impacts on the climate system. Here we estimate this impact on radiation and we study how it depends on the properties and ageing of the plume.
Sergey M. Khaykin, Elizabeth Moyer, Martina Krämer, Benjamin Clouser, Silvia Bucci, Bernard Legras, Alexey Lykov, Armin Afchine, Francesco Cairo, Ivan Formanyuk, Valentin Mitev, Renaud Matthey, Christian Rolf, Clare E. Singer, Nicole Spelten, Vasiliy Volkov, Vladimir Yushkov, and Fred Stroh
Atmos. Chem. Phys., 22, 3169–3189, https://doi.org/10.5194/acp-22-3169-2022, https://doi.org/10.5194/acp-22-3169-2022, 2022
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The Asian monsoon anticyclone is the key contributor to the global annual maximum in lower stratospheric water vapour. We investigate the impact of deep convection on the lower stratospheric water using a unique set of observations aboard the high-altitude M55-Geophysica aircraft deployed in Nepal in summer 2017 within the EU StratoClim project. We find that convective plumes of wet air can persist within the Asian anticyclone for weeks, thereby enhancing the occurrence of high-level clouds.
Ralf Weigel, Christoph Mahnke, Manuel Baumgartner, Antonis Dragoneas, Bärbel Vogel, Felix Ploeger, Silvia Viciani, Francesco D'Amato, Silvia Bucci, Bernard Legras, Beiping Luo, and Stephan Borrmann
Atmos. Chem. Phys., 21, 11689–11722, https://doi.org/10.5194/acp-21-11689-2021, https://doi.org/10.5194/acp-21-11689-2021, 2021
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In July and August 2017, eight StratoClim mission flights of the Geophysica reached up to 20 km in the Asian monsoon anticyclone. New particle formation (NPF) was identified in situ by abundant nucleation-mode aerosols (6–15 nm in diameter) with mixing ratios of up to 50 000 mg−1. NPF occurred most frequently at 12–16 km with fractions of non-volatile residues of down to 15 %. Abundance and productivity of observed NPF indicate its ability to promote the Asian tropopause aerosol layer.
Nuria Pilar Plaza, Aurélien Podglajen, Cristina Peña-Ortiz, and Felix Ploeger
Atmos. Chem. Phys., 21, 9585–9607, https://doi.org/10.5194/acp-21-9585-2021, https://doi.org/10.5194/acp-21-9585-2021, 2021
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We study the role of different processes in setting the lower stratospheric water vapour. We find that mechanisms involving ice microphysics and small-scale mixing produce the strongest increase in water vapour, in particular over the Asian Monsoon. Small-scale mixing has a special relevance as it improves the agreement with observations at seasonal and intra-seasonal timescales, contrary to the North American Monsoon case, in which large-scale temperatures still dominate its variability.
Felix Ploeger, Mohamadou Diallo, Edward Charlesworth, Paul Konopka, Bernard Legras, Johannes C. Laube, Jens-Uwe Grooß, Gebhard Günther, Andreas Engel, and Martin Riese
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We investigate the global stratospheric circulation (Brewer–Dobson circulation) in the new ECMWF ERA5 reanalysis based on age of air simulations, and we compare it to results from the preceding ERA-Interim reanalysis. Our results show a slower stratospheric circulation and higher age for ERA5. The age of air trend in ERA5 over the 1989–2018 period is negative throughout the stratosphere, related to multi-annual variability and a potential contribution from changes in the reanalysis system.
Francesco Cairo, Mauro De Muro, Marcel Snels, Luca Di Liberto, Silvia Bucci, Bernard Legras, Ajil Kottayil, Andrea Scoccione, and Stefano Ghisu
Atmos. Chem. Phys., 21, 7947–7961, https://doi.org/10.5194/acp-21-7947-2021, https://doi.org/10.5194/acp-21-7947-2021, 2021
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A lidar was used in Palau from February–March 2016. Clouds were observed peaking at 3 km below the high cold-point tropopause (CPT). Their occurrence was linked with cold anomalies, while in warm cases, cirrus clouds were restricted to 5 km below the CPT. Thin subvisible cirrus (SVC) near the CPT had distinctive characteristics. They were linked to wave-induced cold anomalies. Back trajectories are mostly compatible with convective outflow, while some distinctive SVC may originate in situ.
Hugo Lestrelin, Bernard Legras, Aurélien Podglajen, and Mikail Salihoglu
Atmos. Chem. Phys., 21, 7113–7134, https://doi.org/10.5194/acp-21-7113-2021, https://doi.org/10.5194/acp-21-7113-2021, 2021
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Following the 2020 Australian fires, it was recently discovered that stratospheric wildfire smoke plumes self-organize as anticyclonic vortices that persist for months and rise by 10 km due to the radiative heating from the absorbing smoke. In this study, we show that smoke-charged vortices previously occurred in the aftermath of the 2017 Canadian fires. We use meteorological analysis to characterize this new object in geophysical fluid dynamics, which likely impacts radiation and climate.
Xiaolu Yan, Paul Konopka, Marius Hauck, Aurélien Podglajen, and Felix Ploeger
Atmos. Chem. Phys., 21, 6627–6645, https://doi.org/10.5194/acp-21-6627-2021, https://doi.org/10.5194/acp-21-6627-2021, 2021
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Inter-hemispheric transport is important for understanding atmospheric tracers because of the asymmetry in emissions between the Southern Hemisphere (SH) and Northern Hemisphere (NH). This study finds that the air masses from the NH extratropics to the atmosphere are about 5 times larger than those from the SH extratropics. The interplay between the Asian summer monsoon and westerly ducts triggers the cross-Equator transport from the NH to the SH in boreal summer and fall.
Keun-Ok Lee, Brice Barret, Eric L. Flochmoën, Pierre Tulet, Silvia Bucci, Marc von Hobe, Corinna Kloss, Bernard Legras, Maud Leriche, Bastien Sauvage, Fabrizio Ravegnani, and Alexey Ulanovsky
Atmos. Chem. Phys., 21, 3255–3274, https://doi.org/10.5194/acp-21-3255-2021, https://doi.org/10.5194/acp-21-3255-2021, 2021
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This paper focuses on the emission sources and pathways of pollution from the boundary layer to the Asian monsoon anticyclone (AMA) during the StratoClim aircraft campaign period. Simulations with the Meso-NH cloud-chemistry model at a horizontal resolution of 15 km are performed over the Asian region to characterize the impact of monsoon deep convection on the composition of AMA and on the formation of the Asian tropopause aerosol layer during the StratoClim campaign.
Adriana Bossolasco, Fabrice Jegou, Pasquale Sellitto, Gwenaël Berthet, Corinna Kloss, and Bernard Legras
Atmos. Chem. Phys., 21, 2745–2764, https://doi.org/10.5194/acp-21-2745-2021, https://doi.org/10.5194/acp-21-2745-2021, 2021
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Using the Community Earth System Model, we simulate the surface aerosols lifted to the Asian tropopause (the ATAL layer), its composition and trend, covering a long-term period (2000–2015). We identify a
double-peakaerosol vertical profile that we attribute to
dryand
convectivecloud-borne aerosols. We find that natural aerosol (mineral dust) is the dominant aerosol type and has no long-term trend. ATAL's anthropogenic fraction, by contrast, shows a marked positive trend.
Corinna Kloss, Gwenaël Berthet, Pasquale Sellitto, Felix Ploeger, Ghassan Taha, Mariam Tidiga, Maxim Eremenko, Adriana Bossolasco, Fabrice Jégou, Jean-Baptiste Renard, and Bernard Legras
Atmos. Chem. Phys., 21, 535–560, https://doi.org/10.5194/acp-21-535-2021, https://doi.org/10.5194/acp-21-535-2021, 2021
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The year 2019 was particularly rich for the stratospheric aerosol layer due to two volcanic eruptions (at Raikoke and Ulawun) and wildfire events. With satellite observations and models, we describe the exceptionally complex situation following the Raikoke eruption. The respective plume overwhelmed the Northern Hemisphere stratosphere in terms of aerosol load and resulted in the highest climate impact throughout the past decade.
Sören Johansson, Michael Höpfner, Oliver Kirner, Ingo Wohltmann, Silvia Bucci, Bernard Legras, Felix Friedl-Vallon, Norbert Glatthor, Erik Kretschmer, Jörn Ungermann, and Gerald Wetzel
Atmos. Chem. Phys., 20, 14695–14715, https://doi.org/10.5194/acp-20-14695-2020, https://doi.org/10.5194/acp-20-14695-2020, 2020
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We present high-resolution measurements of pollutant trace gases (PAN, C2H2, and HCOOH) in the Asian monsoon UTLS from the airborne limb imager GLORIA during StratoClim 2017. Enhancements are observed up to 16 km altitude, and PAN and C2H2 even up to 18 km. Two atmospheric models, CAMS and EMAC, reproduce the pollutant's large-scale structures but not finer structures. Convection is investigated using backward trajectories of the models ATLAS and TRACZILLA with advanced detection of convection.
Mathieu Lachatre, Sylvain Mailler, Laurent Menut, Solène Turquety, Pasquale Sellitto, Henda Guermazi, Giuseppe Salerno, Tommaso Caltabiano, and Elisa Carboni
Geosci. Model Dev., 13, 5707–5723, https://doi.org/10.5194/gmd-13-5707-2020, https://doi.org/10.5194/gmd-13-5707-2020, 2020
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Excessive numerical diffusion is a major limitation in the representation of long-range transport in atmospheric models. In the present study, we focus on excessive diffusion in the vertical direction. We explore three possible ways of addressing this problem: increased vertical resolution, an advection scheme with anti-diffusive properties and more accurate representation of vertical wind. This study focused on a particular volcanic eruption event to improve atmospheric transport modeling.
Silvia Bucci, Bernard Legras, Pasquale Sellitto, Francesco D'Amato, Silvia Viciani, Alessio Montori, Antonio Chiarugi, Fabrizio Ravegnani, Alexey Ulanovsky, Francesco Cairo, and Fred Stroh
Atmos. Chem. Phys., 20, 12193–12210, https://doi.org/10.5194/acp-20-12193-2020, https://doi.org/10.5194/acp-20-12193-2020, 2020
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The paper presents and evaluates a transport analysis method to study the convective injection of air in the upper troposphere–lower stratosphere of the Asian monsoon anticyclone region. The approach is thereby used to analyse the trace gas data collected during the StratoClim aircraft campaign. The results showed that fresh convective air can be injected fast at a high level of the atmosphere (above 17 km), with potential impacts on the stratospheric chemistry of the Northern Hemisphere.
Bernard Legras and Silvia Bucci
Atmos. Chem. Phys., 20, 11045–11064, https://doi.org/10.5194/acp-20-11045-2020, https://doi.org/10.5194/acp-20-11045-2020, 2020
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The Asian monsoon is the most active region bringing surface compounds by convection to the stratosphere during summer. We study the transport pathways and the trapping within the upper-layer anticyclonic circulation. Above 15 km, the confinement can be represented by a uniform ascent over continental Asia of about 200 m per day and a uniform loss to other regions with a characteristic time of 2 weeks. We rule out the presence of a
chimneyproposed in previous studies over the Tibetan Plateau.
Cited articles
AERIS: GEISA: spectroscopic database, http://cds-espri.ipsl.fr/GEISA/AEROSOLS/geisaAerosols.php, last access: 18 June 2025.
Asano, S.: Estimation of the size distribution of Pinatubo volcanic dust from Bishop's ring simulations, Geophys. Res. Lett., 20, 447–450, https://doi.org/10.1029/93GL00512, 1993.
Asher, E., Todt, M., Rosenlof, K., Thornberry, T., Gao, R., Taha, G., Walter, P., Alvarez, S., Flynn, J., Davis, S. M., Evan, S., Brioude, J., Metzger, J., Hurst, D. F., Hall, E., and Xiong, K.: Unexpectedly rapid aerosol formation in the Hunga Tonga plume, P. Natl. Acad. Sci. USA, 120, e2219547120, https://doi.org/10.1073/pnas.2219547120, 2023.
Carn, S. A., Krotkov, N. A., Fisher, B. L., and Li, C.: Out of the blue: Volcanic SO2 emissions during the 2021–2022 eruptions of Hunga Tonga – Hunga Ha'apai (Tonga), Front. Earth Sci., 10, 976962, https://doi.org/10.3389/feart.2022.976962, 2022.
Carr, J. L., Horvath, A., Wu, D. L., and Friberg, M. D.: Stereo Plume Height and Motion Retrievals for the Record-Setting Hunga Tonga-Hunga Ha'apai Eruption of 15 January 2022, Geophys. Res. Lett., 49, e2022GL098131, https://doi.org/10.1029/2022GL098131, 2022.
Duchamp, C., Wrana, F., Legras, B., Sellitto, P., Belhadji, R., and von Savigny, C.: Observation of the aerosol plume from the 2022 Hunga Tonga – Hunga Ha'apai eruption with SAGE III/ISS, Geophys. Res. Lett., 50, e2023GL105076, https://doi.org/10.1029/2023GL105076, 2023.
Hofmann, D. J. and Rosen, J. M.: Sulfuric Acid Droplet Formation and Growth in the Stratosphere After the 1982 Eruption of El Chichón, Science, 222, 325–327, https://doi.org/10.1126/science.222.4621.325, 1983.
Hogan, R. J. and Bozzo, A.: A Flexible and Efficient Radiation Scheme for the ECMWF Model, J. Adv. Model. Earth Sy., 10, 1990–2008, https://doi.org/10.1029/2018MS001364, 2018.
Hummel, J. R., Shettle, E. P., and Longtin, D. R.: A new background stratospheric aerosol model for use in atmospheric radiation models, Tech. Rep., provided by the SAO/NASA Astrophysics Data System, https://ui.adsabs.harvard.edu/abs/1988nbsa.rept.....H (last access: 18 June 2025), 1988.
Iacono, M. J., Delamere, J. S., Mlawer, E. J., Shephard, M. W., Clough, S. A., and Collins, W. D.: Radiative forcing by long-lived greenhouse gases: Calculations with the AER radiative transfer models, J. Geophys. Res., 113, D13103, https://doi.org/10.1029/2008JD009944, 2008.
Khaykin, S., Podglajen, A., Ploeger, F., Grooß, J. U., Tence, F., Bekki, S., Khlopenkov, K., Bedka, K., Rieger, L., Baron, A., Godin-Beekmann, S., Legras, B., Sellitto, P., Sakai, T., Barnes, J., Uchino, O., Morino, I., Nagai, T., Wing, R., Baumgarten, G., Gerding, M., Duflot, V., Payen, G., Jumelet, J., Querel, R., Liley, B., Bourassa, A., Clouser, B., Feofilov, A., Hauchecorne, A., and Ravetta, F.: Global perturbation of stratospheric water and aerosol burden by Hunga eruption, Commun. Earth Environ., 3, 316, https://doi.org/10.1038/s43247-022-00652-x, 2022.
Kloss, C., Sellitto, P., Renard, J.-B., Baron, A., Bègue, N., Legras, B., Berthet, G., Briaud, E., Carboni, E., Duchamp, C., Duflot, V., Jacquet, P., Marquestaut, N., Metzger, J.-M., Payen, G., Ranaivombola, M., Roberts, T., Siddans, R., and Jégou, F.: Aerosol characterization of the stratospheric plume from the volcanic eruption at Hunga Tonga 15 January 2022, Geophys. Res. Lett., 49, e2022GL099394, https://doi.org/10.1029/2022GL099394, 2022.
Kremser, S., Thomason, L. W., von Hobe, M., Hermann, M., Deshler, T., Timmreck, C., Toohey, M., Stenke, A., Schwarz, J. P., Weigel, R., Fueglistaler, S., Prata, F. J., Vernier, J.-P., Schlager, H., Barnes, J. E., Antuña-Marrero, J.-C., Fairlie, D., Palm, M., Mahieu, E., Notholt, J., Rex, M., Bingen, C., Vanhellemont, F., Bourassa, A., Plane, J. M. C., Klocke, D., Carn, S. A., Clarisse, L., Trickl, T., Neely, R., James, A. D., Rieger, L., Wilson, J. C., and Meland, B.: Stratospheric aerosol—Observations, processes, and impact on climate, Rev. Geophys., 54, 278–335, https://doi.org/10.1002/2015RG000511, 2016.
Lacis, A., Hansen, J., and Sato, M.: Climate forcing by stratospheric aerosols, Geophys. Res. Lett., 19, 1607–1610, https://doi.org/10.1029/92GL01620, 1992.
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.
Li, C., Peng, Y., Asher, E., Baron, A. A., Todt, M., Thornberry, T. D., Evan, S., Brioude, J., Smale, P., Querel, R., Rosenlof, K. H., Zhou, L., Xu, J., Qie, K., Bian, J., Toon, O. B., Zhu, Y., and Yu, P.: Microphysical simulation of the 2022 Hunga volcano eruption using a sectional aerosol model, Geophys. Res. Lett., 51, e2024GL108522, https://doi.org/10.1029/2024GL108522, 2024.
Marshall, S. F., Covert, D. S., and Charlson, R. J.: Relationship between asymmetry parameter and hemispheric backscatter ratio: Implications for climate forcing by aerosols, Appl. Optics, 34, 63066311, https://doi.org/10.1364/AO.34.006306, 1995.
Millán, L., Santee, M. L., Lambert, A., Livesey, N. J., Werner, F., Schwartz, M. J., Pumphrey, H. C., Manney, G. L., Wang, Y., Su, H., Wu, L., Read, W. G., and Froidevaux, L.: The Hunga Tonga-Hunga Ha'apai hydration of the stratosphere, Geophys. Res. Lett., 49, e2022GL099381, https://doi.org/10.1029/2022GL099381, 2022.
Norgren, M., Kalnajs, L. E., and Deshler, T.: Measurements of total aerosol concentration in the stratosphere: A new balloon-borne instrument and a report on the existing measurement record, J. Geophys. Res.-Atmos., 129, e2024JD040992, https://doi.org/10.1029/2024JD040992, 2024.
Poli, P. and Shapiro, N. M.: Rapid Characterization of Large Volcanic Eruptions: Measuring the Impulse of the Hunga Tonga Ha'apai Explosion From Teleseismic Waves, Geophys. Res. Lett., 49, e2022GL098123, https://doi.org/10.1029/2022GL098123, 2022.
Russell, P. B., Livingston, J. M., Pueschel, R. F., Bauman, J. J., Pollack, J. B., Brooks, S. L., Hamill, P., Thomason, L. W., Stowe, L. L., Deshler, T., Dutton, E. G., and Bergstrom, R. W.: Global to microscale evolution of the Pinatubo volcanic aerosol derived from diverse measurements and analyses, J. Geophys. Res., 101, 18745–18763, https://doi.org/10.1029/96JD01162, 1996.
Schuster, G. L., Dubovik, O., and Holben, B. N.: Angstrom exponent and bimodal aerosol size distributions, J. Geophys. Res., 111, D07207, https://doi.org/10.1029/2005JD006328, 2006.
Sellitto, P. and Legras, B.: Sensitivity of thermal infrared nadir instruments to the chemical and microphysical properties of UTLS secondary sulfate aerosols, Atmos. Meas. Tech., 9, 115–132, https://doi.org/10.5194/amt-9-115-2016, 2016.
Sellitto, P., Belhadji, R., Kloss, C., and Legras, B.: Radiative impacts of the Australian bushfires 2019–2020 – Part 1: Large-scale radiative forcing, Atmos. Chem. Phys., 22, 9299–9311, https://doi.org/10.5194/acp-22-9299-2022, 2022a.
Sellitto, P., Podglajen, A., Belhadji, R., Boichu, M., Carboni, E., Cuesta, J., Duchamp, C., Kloss, C., Siddans, R., Bègue, N., Blarel, L., Jegou, F., Khaykin, S., Renard, J.-B., and Legras, B.: The unexpected radiative impact of the Hunga Tonga eruption of 15th January 2022, Comm. Earth Environ., 3, 288, https://doi.org/10.1038/s43247-022-00618-z, 2022b.
Sellitto, P., Belhadji, R., Cuesta, J., Podglajen, A., and Legras, B.: Radiative impacts of the Australian bushfires 2019–2020 – Part 2: Large-scale and in-vortex radiative heating, Atmos. Chem. Phys., 23, 15523–15535, https://doi.org/10.5194/acp-23-15523-2023, 2023.
Sellitto, P., Siddans, R., Belhadji, R., Carboni, E., Legras, B., Podglajen, A., Duchamp, C., and Kerridge, B.: Observing the SO2 and sulfate aerosol plumes from the 2022 Hunga eruption with the Infrared Atmospheric Sounding Interferometer (IASI), Geophys. Res. Lett., 51, e2023GL105565, https://doi.org/10.1029/2023GL105565, 2024.
Taha, G., Loughman, R., Colarco, P. R., Zhu, T., Thomason, L. W., and Jaross, G.: Tracking the 2022 Hunga Tonga-Hunga Ha'apai aerosol cloud in the upper and middle stratosphere using space-based observations, Geophys. Res. Lett., 49, e2022GL100091, https://doi.org/10.1029/2022GL100091, 2022.
van de Hulst, H.: Light Scattering by Small Particles, Dover Books on Physics Series, Dover Publications, Mineola, New York, USA, https://books.google.fr/books/about/Light_Scattering_by_Small_Particles.html?id=6ivW_TgIdjIC&redir_esc=y (last access: 18 June 2025), 1957.
Vömel, H., Evan, S., and Tully, M.: Water vapor injection into the stratosphere by Hunga Tonga-Hunga Ha'apai, Science, 377, 1444–1447, https://doi.org/10.1126/science.abq2299, 2022.
Wrana, F., von Savigny, C., Zalach, J., and Thomason, L. W.: Retrieval of stratospheric aerosol size distribution parameters using satellite solar occultation measurements at three wavelengths, Atmos. Meas. Tech., 14, 2345–2357, https://doi.org/10.5194/amt-14-2345-2021, 2021.
Wrana, F., Niemeier, U., Thomason, L. W., Wallis, S., and von Savigny, C.: Stratospheric aerosol size reduction after volcanic eruptions, Atmos. Chem. Phys., 23, 9725–9743, https://doi.org/10.5194/acp-23-9725-2023, 2023.
Zhu, Y., Bardeen, C. G., Tilmes, S., Mills, M. J., Wang, X., Harvey, V. L., Taha, G., Kinnison, D., Portmann, R. W., Yu, P., Rosenlof, K. H., Avery, M., Kloss, C., Li, C., Glanville, A. S., Millán, L., Deshler, T., Krotkov, N., and Toon, O. B.: Perturbations in stratospheric aerosol evolution due to the water-rich plume of the 2022 Hunga-Tonga eruption, Commun. Earth Environ., 3, 248, https://doi.org/10.1038/s43247-022-00580-w, 2022.
Short summary
The Hunga Tonga–Hunga Ha’apai volcano erupted on 15 January 2022, producing the largest stratospheric aerosol perturbation of the last 30 years. Stratospheric volcanic aerosols usually produce a transient climate cooling; these impacts depend on volcanic aerosol composition/size, due to size-dependent interactions with solar/terrestrial radiation. We demonstrate that the Hunga Tonga–Hunga Ha’apai stratospheric aerosols have a larger cooling potential per unit mass than the past climate-relevant El Chichón (1984) and Pinatubo (1991) eruptions.
The Hunga Tonga–Hunga Ha’apai volcano erupted on 15 January 2022, producing the largest...
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