Ice cores provide the best record of volcanic sulfate aerosol emissions in the pre-satellite era, which are used in model simulations to understand the past and future climate hazards of volcanic stratospheric injection. However, the vast majority of ice core recorded events used in climate models are not attributed to known eruptive sources. Therefore, it is necessary to make assumptions of source latitude, plume height, and stratospheric sulfur loading – all variables which impact the climate forcing of an eruption. This is even the case for relatively recent eruptions recorded in ice during the post-industrial era, where cold conditions were experienced by global societies, but no historical records of the culprit eruptions exist.
Using a multi-pronged approach that combines high time resolution sulfur isotope analysis of deposited aerosols and geochemical analysis of microscopic ash particles in polar ice cores, these eruption characteristics can be better constrained. We demonstrate how this multi-method approach has recently aided the investigations into several volcanic eruptions recorded in polar ice cores which are associated with periods of notable climate cooling in the Common Era, including the mysterious 1831 CE eruption. These efforts will improve the volcanic forcing used in model simulations of the climate over the last 2000 years.
How to cite: Innes, H., Hutchison, W., Smith, C., Sugden, P., and Burke, A.: Sulfur isotopes and tephra geochemistry in identifying the volcanic sources of mystery, climate forcing eruptions preserved in ice cores, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20238, https://doi.org/10.5194/egusphere-egu25-20238, 2025.
Explosive volcanic eruptions inject substantial quantities of sulfur gases into the atmosphere significantly influencing global temperatures and hydrological cycles. The formation of sulfate aerosols in the stratosphere following such eruptions can give rise to unusual optical phenomena, including solar dimming, red twilight glows, reddish solar halos, and dark total lunar eclipses. Recently, lunar eclipses have emerged as a valuable tool for reconstructing past stratospheric turbidity and refining the dating of major volcanic eruptions (Guillet et al., 2023).
This study presents a preliminary reconstruction of stratospheric aerosol optical depth (SAOD) from 1600 to 1850 CE, based on descriptions of 80 lunar eclipses documented in over 1,000 historical sources from across Europe. The reconstructed SAOD dataset was compared with bipolar ice core records (Sigl et al., 2015), model-derived aerosol optical depth (Toohey and Sigl, 2017), and climate reconstructions.
Our findings reveal that the darkest lunar eclipses of the past 400 years – occurring in 1601, 1642, 1696 and 1816 – correspond to the largest volcanic eruptions recorded in ice cores and align with significant cooling events in the Northern Hemisphere. This study highlights the potential of lunar eclipse observations to complement ice core data, providing additional, robust information to refine global stratospheric aerosol databases, which are essential for future climate modeling.
This contribution will also discuss plans to extend the dataset to the present day and address the inherent limitations and uncertainties associated with the methodology.
References:
Guillet, S., et al. (2023). Lunar eclipses illuminate timing and climate impact of medieval volcanism. Nature, 616, 90–95.
Sigl, M., et al. (2015). Timing and climate forcing of volcanic eruptions for the past 2,500 years. Nature, 523, 543–549.
Toohey, M., Sigl, M. (2017). Volcanic stratospheric sulfur injections and aerosol optical depth from 500 BCE to 1900 CE. Earth Syst. Sci. Data, 9, 809–831.
How to cite: Boissel, L., Guillet, S., Hureau, C., Lavigne, F., and Dahech, S.: Unveiling volcanic forcing through lunar eclipses: past, present and future perspectives, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12721, https://doi.org/10.5194/egusphere-egu25-12721, 2025.
Caused by intense wildfires, Pyrocumulonimbus generate vigorous convective updrafts that inject biomass burning plumes into the stratosphere. Due to the absorption of solar radiation by carbonaceous aerosols, these plumes are uplifted by radiative heating, up to 35 km altitude, which prolongs their stratospheric residence time. In this study we model the self-lofting of these stratospheric plumes as well as their radiative impact.
In the first step, we focus on the physical properties of these plumes and the radiative modeling of their self-lofting. Measurement-based determination of the Single Scattering Albedo (SSA) for stratospheric aerosols is however a challenging task. We thus attempt to constrain the SSA using a combination of radiative transfer modeling and observations from both ground-based and CALIPSO space-borne lidars, as well as use of OMPS-LP extinction profiles. The DIScrete Ordinate Radiative Transfer (DISORT) model, as part of Atmospheric Radiative Transfer Database for Earth Climate Observation (ARTDECO) numerical tool is employed to reproduce the observed self-lofting rate of the plume for varying properties of the plume. We find that the aerosol optical depth and the geometrical thickness of the plume are crucial parameters to model the self-lofting. We also take into account the variations of the underlying cloud cover and surface albedo to better model the self-lofting mechanism.
In the second step, having assessed the SSA, we estimate the radiative forcing induced by these plumes at the top and the bottom of the atmosphere. This method is applied to the Pacific Northwest Event (PNE) wildfire outbreak in August 2017 and the Australian New Year Super Ourbreak (ANYSO) in 2019/20. The results are then compared with previous studies. Finally, we compare the radiative forcing efficiencies of stratospheric smoke with that of stratospheric aerosols from moderate volcanic eruption on local and global scales.
How to cite: Lebrun, R., Derimian, Y., Ravetta, F., Bureau, J., and Khaykin, S.: Self-lofting and radiative forcing of stratospheric aerosol from major wildfires and how it compares to volcanic eruptions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-11701, https://doi.org/10.5194/egusphere-egu25-11701, 2025.
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
How to cite: Podglajen, A., Tran, D. D., Sellitto, P., Duchamp, C., Legras, B., Randel, W., and Starr, J.: Diabatic Heating Rates and Mesoscale Vortices in Stratospheric Volcanic Plumes: Insights from the 2022 Hunga and 2019 Raikoke plumes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19899, https://doi.org/10.5194/egusphere-egu25-19899, 2025.
Volcanic eruptions release aerosols into the stratosphere, which can trigger a wide range of climate responses across different temporal and spatial scales. However, the physical processes through which volcanic forcing leads to long-term global and regional cooling remain inadequately explored. Specifically, the climate responses following a series of intense volcanic eruptions before the Holocene remain insufficiently understood. The conditions during such past climates were vastly different from today’s, suggesting that potential amplifying feedbacks may also have differed. Using fully glacial, deglacial and pre-industrial boundary conditions, we conducted a suite of experiments with the Hadley Centre Coupled Model Version 3 and the Max Planck Institute's Earth System Model, forced with idealised volcanic eruption clusters, to investigate the long-term post-eruption sea surface temperature and sea ice responses in the North Atlantic. We find more intense and longer-lasting cooling in the subpolar North Atlantic in the fully glacial state compared to the other climate states. We explore the physical processes driving this cooling and how differences in the representation of upper-ocean conditions across the two climate models lead to model-dependent results.
How to cite: Dutta, D., Hopcroft, P., Muschitiello, F., Andreasen, L., Aubry, T., Zhang, X., Timmreck, C., and Zanchettin, D.: Climate Responses to Volcanic Eruption Clusters in the North Atlantic Under Different Boundary Conditions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19434, https://doi.org/10.5194/egusphere-egu25-19434, 2025.
The Hunga eruption, January 2022, injected ~150 Tg of water vapour into the sub-tropical mid-stratosphere, unprecedented in the satellite era. The effects of the Hunga water vapour on the heterogeneous chemistry in the Antarctic stratosphere did not occur in the 2022 season, with the vortex edge a barrier to transport to high southern latitudes, until vortex break-up. Here, we analyse chlorine activation and ozone loss impacts starting with the 2023 vortex, and find these effects were not uniform throughout the vortex, and were limited by widespread mid-winter dehydration that occurs in the Antarctic each year, mainly in the colder “vortex core” region, via ice-containing polar stratospheric clouds (PSCs).
Heterogeneous, chlorine-activating reactions on PSC surfaces play a key role in polar stratospheric ozone depletion and the formation of the seasonal Antarctic ozone hole. Stratospheric water vapour is one of the key factors in PSC formation; thus, the water vapour enhancement from Hunga is likely to impact PSC occurrence and therefore may increase the ozone depletion. However, the effects may vary between different regions of the vortex. The core region experiences the lowest temperatures, frequently reaching the threshold for ice PSCs, and the most extensive dehydration (in the lower stratosphere) over much of the vortex season. In contrast, the edge region is more sunlit, less cold, and experiences less extensive dehydration than the core, meaning there is scope for different chemical impacts in this region. Overall, the Hunga eruption offers a unique opportunity to test our understanding of how a large-scale increase in water vapour impacts polar ozone, and how the vortex structure influences the timing and magnitude of the effects.
Here we use the TOMCAT three-dimensional chemical transport model to investigate the impacts of the Hunga water vapour on Antarctic stratospheric ozone and associated heterogeneous chlorine reactions, comparing the 2023 and 2024 Antarctic vortex seasons. We find that the enhanced water vapour raised PSC formation temperatures, resulting in earlier formation and, consequently, an earlier onset of the heterogeneous chemistry and chlorine activation. However, it is evident that the vortex structure has some influence on the impact. Compared to a control simulation without Hunga, the effect on the edge region occurs throughout the PSC season, whereas the core, due to effective dehydration, experiences large differences at the beginning and end of the season, with minimal differences in between.
We will also briefly summarise the impact of Hunga water vapour on Arctic springtime ozone in recent years, including 2025. The effect of Hunga in the Arctic has so-far been limited by the timing of the water transport (2022/23) and a series of stratospheric warming events (SSWs) (2023/24). However, the 2024/25 Arctic winter began colder than usual in December/January. Therefore, effects of the Hunga water vapour may be more pronounced during this Arctic winter subject to any warming events still to come.
How to cite: Heddell, S., Chipperfield, M., Dhomse, S., Mann, G., Feng, W., Yoshioka, M., and Zhou, X.: The impact of the 2022 Hunga water-rich eruption on polar stratospheric clouds, chlorine activation and ozone depletion, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18228, https://doi.org/10.5194/egusphere-egu25-18228, 2025.
Volcanic sulfate injections into the stratosphere following major eruptions are able to modulate climate, as demonstrated by the well-documented 1991 Mt. Pinatubo eruption. Understanding the climate response to such events is critical, especially in the context of potential solar radiation management strategies to counteract climate change. An important part of volcanic impact on the atmospheric system originates from volcano-induced lower stratospheric heating that leads to changes in stratospheric circulation and transport and possibly in stratosphere-troposphere coupling and regional tropospheric circulation. Previous modeling studies have shown diverse results concerning these effects, partly due to model uncertainties and differences in simulation setup or study design, such as prescribed aerosols and/or chemistry, while the feedbacks between these system components were shown to be significant.
This study evaluates the tropical stratospheric temperature response to the Mt. Pinatubo eruption using eight global models with interactive aerosol microphysics. All models adhered to the Historical Eruptions SO2 Emission Assessment (HErSEA) protocol under the Interactive Stratospheric Aerosol Model Intercomparison Project (ISA-MIP). We focus on the uncertainties related to initial SO2 emission amounts and injection heights. Results reveal that while models exhibit consistent sensitivity to initial SO2 amounts and injection heights, the magnitude and extent of the stratospheric temperature response vary. By comparing model outputs and observations, this study enhances our understanding of individual model performances and the current multi-model uncertainty range and provides critical insights for future climate impact assessments of volcanic eruptions.
How to cite: Perny, K., Arsenovic, P., Brühl, C., Dhomse, S., Kuchar, A., Laakso, A., Mann, G., Niemeier, U., Pitari, G., Quaglia, I., Rieder, H., Sekiya, T., Sukhodolov, T., Tilmes, S., Timmreck, C., and Visioni, D.: Assessing the stratospheric temperature response to volcanic sulfate injections: insights from a multi-model framework, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3677, https://doi.org/10.5194/egusphere-egu25-3677, 2025.
The release of stratospheric aerosols from major volcanic eruptions induces large-scale global and regional climate impacts through radiative perturbations. The extent of these impacts depends on the season, aerosol-cloud distribution, the height reached by the ejections, and the latitude of the eruption, causing symmetrical and asymmetrical forcing. Previous studies have linked some severe Sahel drought conditions during the 20th century from two to four seasons of post-eruption feedback. However, a detailed analysis of the causal mechanism through the complex teleconnections driving changes of the African monsoon and its atmospheric dynamics in response to the volcanic eruption is yet to be addressed. Besides, the interest in the deliberate stratospheric injection of sulfate aerosols as a Solar Radiation Management (SRM) technique has increased due to the difficulties of limiting the global mean temperature to 1.5 or 2.0 °C above the Pre-industrial level. This implies the need to investigate the associated hydro-climate changes in response to such climate change solution techniques across Africa. In this study, we explore the response of the African monsoon and its driving teleconnections changes to past volcanic eruptions to better understand the potential climate impacts of future eruptions and even further to the proposed SRM geoengineering. Since larger and wider varieties of eruptions occurred in the last millennium compared to the 20th century, we use the past millennium's natural external volcanic forcings as an analog to explore the dynamics feature and associated teleconnections of the African monsoon. We rely on the varied experimental simulation outputs of the state-of-the-art Earth System Models that participated in the sixth phase of the Coupled Model Intercomparison Project (CMIP6). More specifically, we use the models that simulated the past millennium (PMIP4; Jungclaus et al., 2017), volcanic forcing experiments (VolMIP; Zanchettin et al., 2016), and stratospheric aerosol geoengineering experiments (GEOMIP; Jones et al., 2021). Overall, the analyzed responses from the modelling perspective provide an overview of the impact of volcanic forcings across Africa in the past, present, and future climates.
How to cite: Arthur, F. and Boateng, D.: The response of African monsoons to the symmetric and asymmetric Volcanic eruptions in past and future climate, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16818, https://doi.org/10.5194/egusphere-egu25-16818, 2025.
The January 2022 eruption of Hunga Tonga-Hunga Ha’apai (HTHH) injected unprecedented amounts of water vapour (WV) and sulfur dioxide (SO2) into the stratosphere, significantly impacting the Earth's climate system. Utilizing the Earth System Model SOCOLv4, this study investigates the dynamical implications of the middle-atmosphere disturbances caused by HTHH. A novel dynamical pathway linking water-rich volcanic eruptions to surface climate was identified. The excess stratospheric WV led to significant anomalies in atmospheric circulation, particularly influencing the Northern Hemisphere polar vortex (PV). The findings highlight the potential for such eruptions to modulate the stratospheric PV and subsequent surface climate through altered temperature gradients and weakened polar-night jets, contributing to sudden stratospheric warmings (SSWs). Furthermore, we explain the mechanism dependency on model-projected forcing and its relation to identified biases common also in other chemistry-climate models.
How to cite: Kuchar, A., Sukhodolov, T., Chiodo, G., Jörimann, A., Kult-Herdin, J., Rozanov, E., and Rieder, H.: Modulation of the Northern Polar Vortex by the Hunga Tonga-Hunga Ha’apai Eruption and Associated Surface Response, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10357, https://doi.org/10.5194/egusphere-egu25-10357, 2025.
The record-breaking January 2022 Hunga eruption raised questions regarding the large amount of water vapor (150 Tg) reaching the stratosphere and the surprisingly less amount of ash detected. The emission of such large amount of water vapor in numerical models poses its own challenges and limitations. From ground-based estimates of emitted ash, the emitted fine ash is estimated to be around 17-34 Tg, however, only up to 1-2 Tg was present in the atmosphere which indicates an extremely fast removal of ash. This study investigates the role of various aerosol dynamical processes and hence, the accelerated removal of ash particles. This is done through emission of ash, water vapor, SO2 and NaCl in the ICOsahedral Nonhydrostatic model with Aerosols and Reactive Tracers (ICON-ART). Three possible pathways of faster growth and consequently, removal of particles, are explored in this study. These include (1) ash particle growth due to coagulation with sea salt and further growth by water owing to the highly hygroscopic nature of sea salt, (2) fast wet aggregation of particles during the plume rise, and (3) activation of particles to large hydrometeors. The results emphasize the importance of including sea salts emission along with ash and SO2 in modelling studies and the subsequent effects on aerosol dynamical processes.
How to cite: Chopra, S., Bruckert, J., and Hoshyaripour, G.: Rapid Ash Removal in the 2022 Hunga Volcano Plume: The Role of Aerosol Microphysical Processes, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3629, https://doi.org/10.5194/egusphere-egu25-3629, 2025.
Using the chemistry-climate model EMAC with nudged tropospheric meteorology, we show that organic carbon injected into the stratosphere through forest fire-related pyro-cumulonimbi enhances heterogeneous chlorine activation due to enhanced solubility of HCl in particles containing organic acids and a larger aerosol surface area. After the 2019/2020 Australian mega-bushfires, the upward transport of the pollution plume led to enhanced ozone depletion in the Southern hemispheric lower stratosphere, in agreement with AURA-MLS satellite observations. It reduced total ozone in 2020 and 2021 by up to 28 DU around 70oS, accompanied by a dynamic reduction in August 2020 from the lofting of smoke-filled vortices, reaching 24 DU (total about 40 DU near 65oS). The eruption of Hunga Tonga in January 2022 led to a reduction of total ozone in the entire Southern hemisphere, exceeding 10 DU south of about 55oS in Austral spring of 2022 and 2023. The water vapor injection by the volcano modified only the vertical distribution of ozone loss.
The absorbing aerosol from the combined Australian and Canadian forest fire emissions in 2019/2020 caused the largest perturbation in stratospheric optical depth (e.g., seen in OSIRIS data) since the eruption of Pinatubo. It changed the instantaneous stratospheric aerosol forcing -derived at the top of the atmosphere- from -0.2 W/m2 to +0.3 W/m2 in January 2020. In January 2022, the remaining effect was about 0.05 W/m2, reducing the negative forcing by volcanoes. The computed global aerosol radiative forcing caused by the Hunga Tonga eruption in 2022 was about -0.12 W/m2, decreasing to -0.06 W/m2 by December 2023, dominated by the change in stratospheric sulfate aerosols. The positive forcing of the injected water vapor was small (in agreement with other models).
How to cite: Brühl, C., Kohl, M., Lelieveld, J., Rieger, L., and Santee, M.: Radiative forcing and stratospheric ozone changes due to major forest fires and recent volcanic eruptions including Hunga Tonga, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3642, https://doi.org/10.5194/egusphere-egu25-3642, 2025.
In the future, in a warmer world due to anthropogenic greenhouse gas forcing, the impact of natural forcing on climate could change dramatically. However, it is not yet clear how strong a volcanic forcing as in the early 19th century will affect future climate. Previous studies show both an amplification of the surface cooling response, mainly due to an increase in upper ocean stability, and a weakening of the volcanic-induced surface cooling in a future climate state due to a reduced effective volcanic aerosol radiative forcing.
To assess how different climate states affect the climate response to volcanic forcing, we have performed MPI-ESM ensemble experiments under historical, 4xCO2 and present-day conditions with volcanic forcing equivalent to that of the early 19th century. On these simulations, we have also tested explicable artificial intelligence methods to see if they are able to achieve a similar skill for specific fingerprints in the temperature record when the boundary conditions are very different from the present, as in the case of a 4xCO2 scenario.
We find that different changes in Arctic sea ice cover and northern hemisphere winter sea level pressure are induced by the same volcanic forcing under distinct climate states, while the large-scale average temperature response shows no significant differences. The volcanic fingerprint in the surface temperature pattern is similar for all climate states for large volcanic eruptions in the first post-volcanic year, while the background state becomes relevant afterwards, as well as for smaller eruptions
How to cite: Timmreck, C., Fang, S.-W., Meuer, J., Jungclaus, J., Kadow, C., and Schmidt, H.: Will the climate response to volcanic eruptions change in the future?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6342, https://doi.org/10.5194/egusphere-egu25-6342, 2025.
Various sets of metrics have been used to rank the performance of CMIP6 models for a variety of purpose.
Here we present a potential set of metrics that would simplify a similar ranking for the purpose of evaluating the skill of climate models with a fully resolved stratosphere, including dynamics, chemistry, and aerosol microphysics in representing perturbations to stratospheric composition, such as past volcanic eruptions, as a first step to determine the reliability in future cases such as new volcanic eruptions or Stratospheric Aerosol Intervention.
Our purpose is to find metrics that include available observations of large and medium volcanic eruptions, such as Mt. Pinatubo in 1991, and that also consider the uncertainties in past retrievals, and that are representative of models skills across time (i.e. considering not just the initial plume development, but also the e-folding time and ultimate fate of the aerosol cloud) and space. We include metrics that consider aerosol spatial distribution, local and global size distribution and chemical properties through surface area density.
Our set of metrics could be of great use as more models in CMIP7 start including prognostic aerosols schemes and higher tops, and could inform future strategies for better observations of the stratospheres, as well as identify necessary variables to be requested by CMIP as part of the data requests prioritization for the Atmosphere Working Group.
How to cite: Visioni, D. and Quaglia, I.: Developing a set of simple metrics to evaluate the performance of models with interactive stratospheric aerosols, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10745, https://doi.org/10.5194/egusphere-egu25-10745, 2025.
Projecting the chemistry-climate effects of stratospheric aerosols within general circulation models (GCMs) requires simulating multiple coupled processes, which are subject to large uncertainties. Here, we utilize an updated version of the GFDL Earth System Model (GFDL-ESM4.1) with an interactive representation of the stratospheric sulfur cycle to explore the state dependence of stratospheric aerosol chemistry-climate impacts in GFDL-ESM4.1. Understanding this state dependence is crucial for assessing the volcanic chemistry-climate impacts under global warming and is beneficial for evaluating the effectiveness of stratospheric aerosol injection as a geoengineering approach.
We first conduct a baseline simulation from 1989 to 2014, driven by observed sea-surface temperature and sea ice, and including volcanic emissions of sulfur into the stratosphere. Then, we perform sensitivity simulations with sea surface temperature uniformly increased or decreased by 4K to examine the chemistry-climate impacts of stratospheric aerosols under warmer and cooler climate conditions. Our results show that stratospheric aerosol optical depth (SAOD) and burden are sensitive to surface temperature, in our simulations with prescribed volcanic injection heights. In a warmer climate, the accelerated Brewer-Dobson Circulation causes a rapid decay of stratospheric sulfate lifetime and lower SAOD in the 3 years following a the Mt. Pinatubo eruption. The warmer climate also produces a continuously lower SAOD during periods without major eruptions. Changes in SAOD from major eruptions are more sensitive to warming (approximately -11%/K) than to cooling (approximately -5%/K) from the baseline climate. Moreover, the lower SAOD from major eruptions is compensated by higher natural aerosol emissions under a warmer climate, buffering the changes in total AOD. Combined changes—decreased SAOD, albedo feedback, and increased natural aerosols emissions—result in an increase of clear-sky shortwave radiative effect by up to ~2.8 W/m2 in a warmer climate compared to the baseline. We will also explore the follow-on effects on ozone chemistry from the sensitivity of stratospheric aerosols to surface temperature in GFDL-ESM4.1. These results highlights the importance of the interactive sulfur cycle approach in GCMs.
How to cite: Zhang, S., Naik, V., Horowitz, L., and Gao, Y.: State dependence of stratospheric aerosol chemistry-climate impacts in GFDL-ESM4.1, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14519, https://doi.org/10.5194/egusphere-egu25-14519, 2025.
Stratospheric volcanic aerosol can have major impacts on the global climate. However, these impacts are eruption specific, as they critically depend on the characteristics of the eruption, such as magnitude, location and timing. Towards understanding these criticalities, only a handful of studies have either assessed the effects of eruptions at distinct times throughout the year or the location of eruption. To our knowledge, no study has hitherto considered the combined of the timing and location of an eruption. Here we investigate variations in the impact of volcanic eruptions linked on the timing of the eruption in relation to the seasons of the year and the location (Northern or Southern Tropical eruption), focusing on ENSO dynamics. In doing so, we use the Norwegian Earth System Model (NorESM) to perform a set of sensitivity experiments in which the tropical volcanic eruptions are set to go off at the beginning of each season. These experiments are meant to shed light on the role of the season in shaping the ENSO response to volcanic eruption, elucidating the nuanced role of volcanic forcing in modulating ENSO variability and enhancing our predictive capabilities of this influential climate phenomenon. In our contribution, we will describe first results from our experiments showing how boreal spring and summer Northern Tropical eruptions lead to El Niño-like conditions in the winter of the eruption, followed by strong La Niña conditions. On the other hand, boreal fall and winter eruptions causes a weak La Niña on the first 6-8 months, followed by El Niño conditions in the winter after the eruption. For Southern Tropical eruptions the response is muted and only fall and winter eruptions show El Niño conditions in the second winter of the eruption. To better understand the different responses, we will also interpret the model results within the framework of a simple delayed oscillator of ENSO.
How to cite: Pausata, F. S. R. and Zanchettin, D.: ENSO response to tropical volcanic eruptions: the role of the season, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12390, https://doi.org/10.5194/egusphere-egu25-12390, 2025.
The Hunga Tonga-Hunga Ha’apai (Hunga) volcanic eruption in January 2022 injected a substantial amount of water vapor and a moderate amount of SO2 into the stratosphere. Both satellite observations in 2022 and subsequent chemistry-climate model simulations forced by realistic Hunga perturbations reveal large-scale cooling in the Southern Hemisphere (SH) tropical to subtropical stratosphere following the Hunga eruption. This study analyzes the drivers of this cooling, including the distinctive role of anomalies in water vapor, ozone, and sulfate aerosol concentration on the simulated climate response to the Hunga volcanic forcing, based on climate simulations with prescribed chemistry/aerosol. Simulated circulation and temperature anomalies based on specified-chemistry simulations show good agreement with previous coupled-chemistry simulations and indicate that each forcing of ozone, water vapor, and sulfate aerosol from the Hunga volcanic eruption contributed to the circulation and temperature anomalies in the Southern Hemisphere stratosphere. Our results also suggest that 1) the large-scale stratospheric cooling during the austral winter was mainly induced by changes in dynamical processes, not by radiative processes, and that 2) ozone’s radiative feedback contributed to the prolonged cold temperature anomalies in the lower stratosphere (~70 hPa level) and hence to long lasting cold conditions of the polar vortex.
How to cite: Yook, S., Solomon, S., and Wang, X.: The Impact of 2022 Hunga Tonga-Hunga Ha’apai (Hunga) Eruption on Stratospheric Circulation and Climate, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12900, https://doi.org/10.5194/egusphere-egu25-12900, 2025.
The presence of aerosols in the stratosphere alters the spectral shape, the amount and the spatial distribution of the solar light that reaches the Earth surface. Such changes in surface solar radiation have been discussed in a few studies, but the role of the underlying tropospheric aerosol layer in the presence of stratospheric aerosols has not been considered. In this study we investigate the changes in the direct and global spectral surface solar irradiances following the extremely intense volcanic eruption (VEI=6) of Mount Pinatubo (15°N, 120°E) in June 1991. The eruption of Mount Pinatubo ejected massive loads of sulphate and ash particles into the stratosphere, which covered the entire globe after three weeks and then remained in the stratosphere for several months. In the aftermath, major perturbations of the stratospheric ozone layer and the near-surface temperature have been documented. Here, we provide model-derived stratospheric aerosol optical properties, constrained by ground-based and airborne remote sensing and in-situ data, to the radiative transfer model libRadtran to calculate the spectral surface solar irradiance in the wavelength range 350 – 750 nm. Radiative transfer simulations have been performed for two European sites where in situ measurements of the aerosol extinction profile were available a few months after the eruption, assuming different concentrations and types of tropospheric aerosols present in the atmosphere along with the overlying stratospheric volcanic layers, as well as different solar zenith angles. Changes in the spectral composition and the distribution of surface solar radiation in the considered spectral range play a key role in many biological processes (e.g., photosynthesis), as well as in solar energy production. Thus, our results provide insights on how such processes could be impacted after future volcanic eruptions or under solar radiation modification scenarios.
Acknowledgements: This work has been supported by the action titled “Support for upgrading the operation of the National Network for Climate Change (CLIMPACT II)”, funded by the Public Investment Program of Greece, General Secretary of Research and Technology/Ministry of Development and Investments.
How to cite: Fountoulakis, I., Misios, S., Gialitaki, A., Gkikas, A., Amiridis, V., Kampouri, A., Kouklaki, D., Kazantzidis, A., Eleftheratos, K., Kourtidis, K., Rémy, S., Mayer, B., and Zerefos, C. S.: Changes in the spectral composition of surface solar radiation under the presence of stratospheric aerosols: a case study for the Pinatubo eruption, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-13646, https://doi.org/10.5194/egusphere-egu25-13646, 2025.
The 2022 Hunga Tonga-Hunga Ha'apai (HTHH) volcanic eruption injected around 150 Tg water vapor into the stratosphere. Using Microwave Limb Sounder (MLS) water vapor measurement, this study provides the first evaluation of the HTHH-induced stratospheric water vapor (SWV) products revealed by the ERA5, MERRA2 and M2-SCREAM reanalyses. Results show that ERA5 and MERRA2 underestimate the SWV mass compared to MLS observations, while M2-SCREAM shows good consistency not only in the magnitude but also in the transport and depletion details. M2-SCREAM also perform well in the estimation of the long-term trend of SWV mass, while ERA5 and MERRA2 both overestimate the trend, suggesting the potential value of M2-SCREAM in estimating the long-term climatic influence of HTHH eruption. The extent to which the assimilation of SWV contributes to the significant discrepancies observed between M2-SCREAM and ERA5 as well as MERRA2 offers valuable insights for enhancing the numerical simulation of reanalyses.
How to cite: Li, Y., Zhou, X., Zhang, W., Gao, C., Chen, Q., and Feng, W.: Can Reanalysis Datasets Show Unprecedented Stratospheric Water Vapor After the Hunga Tonga-Hunga Ha’apai Eruption?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15396, https://doi.org/10.5194/egusphere-egu25-15396, 2025.
The 2022 Hunga volcanic eruption, which injected approximately 150 Tg of water vapour directly into the stratosphere, was an unprecedented event and provided a basis for a multitude of middle atmospheric studies. Changes in water vapour in the stratosphere and above affect the chemical composition of the middle atmosphere, the heating and cooling rates in this region, and the longwave downwelling fluxes at the surface.
In this study, we focus on the radiative impact of the changes in the water vapour mixing ratio at two locations where continuous profiling of water vapour has been performed using high-spectral-resolution microwave radiometers. The radiative transfer schemes included in the Whole Atmosphere Community Climate Model (WACCM-X (SD)) are compared to a line-by-line radiative transfer scheme from the Atmospheric Radiative Transfer Simulator (ARTS) to assess the accuracy of these radiative transfer schemes in analysing differences in heating rates and fluxes in the middle atmosphere.
How to cite: Bell, A., Stober, G., Shi, G., Liu, H., and Murk, A.: Radiative Effects of Hunga Volcanic Eruption in the Middle Atmosphere: A Model and Observation-Based Analysis, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16379, https://doi.org/10.5194/egusphere-egu25-16379, 2025.
The lifetime of sulphur in the strartosphere depends on volcanic emission parameters and aerosol microphysical processes, as well as on particle transport. These processes interact and determine the particle size and optical depth of the volcanic cloud.
While tracer transport, via advection and turbulence, affects mixing and dilution, it feeds back onto the aerosol concentration and the microphysical processes. At the same time, the aerosols absorb terrestrial radiation, which heats the stratospheric aerosol layer and affects transport. Thus, all processes interact, feedback to each other and determine the concentration and particle size of the aerosol.
To disentangle the role of aerosol microphysical processes and heating from the role of transport in aerosol evolution, we introduced a passive tracer. This allows us to determine the impact of the grid size on stratospheric dynamics and tracer transport. Therefore, we added emissions of the gas SF6 (sulphur hexafluoride) to ICON-XPP. SF6 is inert in the troposphere and lower stratosphere and is emitted in industrial production. This allows us to compare the simulated distribution of SF6 with observations.
Comparison with observations allows us to better understand the transport processes in the model. Important for the transport of a volcanic cloud is the velocity of the vertical transport in the tropical pipe or the meridional transport to higher latitudes. Since previous studies have shown a dependence of the transport in the tropical pipe on the model grid, we have performed simulations with different horizontal and vertical resolutions to determine the role of the grid. We had to tune the model for the different resolutions. In the process, we obtained different dynamical states in the lower tropical stratosphere, the region of the quasi-biennial oscillation (QBO). For example, we got only easterly or only westerly jets in the lower tropical stratosphere. These different jets allow us to see the effect of the QBO on the transport of SF6.
How to cite: Niemeier, U., Kornblueh, L., and Schneidereit, A.: The dependence of tracer transport on grid refinement, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16471, https://doi.org/10.5194/egusphere-egu25-16471, 2025.
Large volcanic eruptions are a source of climate variability, affecting global temperatures and precipitation. The hydrology of the Indian monsoon region is particularly sensitive to volcanic forcing. Previous studies have focused on the seasonal mean response of the Indian monsoon to eruptions. Here, we investigate the changes to the onset of the monsoon, which is an important characteristic that impacts the water budget of the region. Using large Earth System ensemble simulations with idealised model eruptions that inject 40 Tg of sulphur into the stratosphere at varying latitudes, we observe changes in onset date by a few weeks compared to an unforced case. We find that the date of onset of the Indian summer monsoon is strongly dependent on the eruption latitude. Our results show a delayed (advanced) Indian monsoon onset for a Northern (Southern) Hemispheric eruption. However, the internal variability of the monsoon system also influences the onset. We find that existing mechanisms linking internal variability to monsoon onset are insufficient to explain the onset changes observed due to volcanic forcings. Based on the Low-Level Jet (LLJ) and ITCZ frameworks, we propose a new mechanism of monsoon onset variation due to volcanic eruptions. We show that not just a strengthening LLJ, but also an increased moisture flux into the Indian monsoon region triggers an earlier onset.
How to cite: Iyer, S., Guenther, M., Jalihal, C., and Timmreck, C.: Sensitivity of Monsoon Onset to Idealised Volcanic Forcing, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17973, https://doi.org/10.5194/egusphere-egu25-17973, 2025.
The stratospheric aerosol layer is a key component of the climate system through its impact on radiation, chemistry and climate. While satellite observations have observed this layer for more than 4 decades through solar occultation, limb scatter and lidar techniques, we still lack in situ measurements to fully understand how its spatial and temporal evolution vary through the influence of multiple sources. Long-term balloon measurements of stratospheric aerosols are available mostly at mid-latitudes and do not cover the tropics, a key region that largely affects the supply and the transport of stratospheric aerosols at global scales. Our team has deployed at multiple locations including Australia, India, Brazil since the past decade to study the impacts of volcanic eruptions, the Asian monsoon and PyroCbs on the stratosphere through in situ measurements. Leveraging on this experience, we believe that the next step is to conduct regular balloon-borne observations through a new network, the Balloon Network for stratospheric aerosol Observation (BalNeO). During this presentation, we will describe the overall objectives of BalNeO and show some preliminary results.
How to cite: Vernier, J.-P.: Balloon Network for stratospheric aerosol Observations (BalNeO): A new network to monitor the stratosphere, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18647, https://doi.org/10.5194/egusphere-egu25-18647, 2025.
Northern Eurasian winter warming (NEWW) is reported both in the observation and reconstruction following major tropical volcanic eruptions. However, current climate models struggle to accurately simulate this warming phenomenon, posing challenges to fully understand and validate this distinct climate response amidst the general trend of volcano-induced global cooling. Here we show that, the persistent volcanic cloud from summer to late autumn and the associated warming of the mid-latitude stratosphere plays a pivotal role in triggering NEWW. The role of winter aerosols is demonstrated by sensitivity simulations with updated volcanic forcing of the 1783 Icelandic Laki eruption, supported by two recently available temperature reconstructions, and reversely verified by model results of various eruptions without substantial cold season aerosol loadings. The abnormal mid-latitude stratospheric warming enhances the meridional temperature gradient, strengthens the polar vortex, alters both horizontal and vertical energy redistribution that contributed to NEWW. The findings help to reconcile the model-observation discrepancy of post-eruption winter climate responses, and point to the critical role of stratosphere-troposphere coupling in responding and redistributing the radiative perturbation.
How to cite: Yang, L., Gao, C., and Liu, F.: Winter Warming in Northern Eurasia Following the 1783 Laki Volcanic Eruption, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18827, https://doi.org/10.5194/egusphere-egu25-18827, 2025.
Tropical volcanic eruptions are significant drivers of climate variability, inducing North Atlantic Oscillation (NAO)-like circulation changes that lead to high-latitude Eurasian winter warming and amplified cooling in the Middle East and North Africa (MENA). However, recent studies have raised concerns about the robustness of this post-eruption NAO-like response, suggesting that its regional impacts on Eurasia and MENA could be linked to coexisting El Niño-like variability rather than volcanic-induced NAO variability. To address this gap, this study utilizes the high-top MIROC6 coupled model to examine the roles of NAO and ENSO in shaping regional climate dynamics over MENA following tropical volcanic events. Our findings reveal that post-eruption winter responses are primarily driven by NAO, with El Niño-like conditions amplifying MENA cooling but not initiating it. In summer, volcanic aerosols weaken the Hadley circulation's updraft branch (i.e., ITCZ), leading to tropical warming and drying, with further amplification by ENSO interactions. These results validate MIROC6's effectiveness in simulating volcanic impacts and offer critical insights for interpreting climate models and informing post-eruption climate policies.
How to cite: Dogar, M. M., Watanabe, S., and Fujiwara, M.: Investigating the Climatic Impacts of Volcanic Eruptions over Eurasia and MENA Using the MIROC6 Coupled Climate Model, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-18860, https://doi.org/10.5194/egusphere-egu25-18860, 2025.
Stratospheric aerosols play a crucial role in Earth's radiative balance and atmospheric chemistry. Their sources and properties are influenced by various factors, including volcanic eruptions, biomass burning (PyroCbs), and the Asian Tropopause Aerosol Layer (ATAL). The ATAL, a prominent feature of the Asian Summer Monsoon (ASM), extends from the eastern Mediterranean across India to western China at altitudes of 13-18 km.
Recent volcanic eruptions have significantly impacted the stratosphere, with varying characteristics such as the magnitude and altitude of the eruption, the injected mass, and the resulting aerosol composition. These eruption characteristics, combined with the dynamics of the Asian Monsoon Anticyclone (AMA), and the pre-existing chemical state of the ATAL, contribute to complex and diverse aerosol properties within this region.
The Balloon measurement campaign of the ATAL (BATAL) project utilizes balloon-borne instruments to investigate the optical, physical, and chemical properties of the ATAL. Since its inception a decade ago, BATAL has employed optical particle counters, balloon-borne radiosondes, and aerosol collectors to characterize ATAL aerosols. These measurements are further complemented by satellite and ground-based lidar observations to enhance our understanding of aerosol sources and transport mechanisms. Understanding the different sources of stratospheric aerosols over Asia is critical to differentiate the impacts of anthropogenic and natural aerosols on the climate and monsoon hydrological cycle.
In the summer of 2024, after a four-year hiatus due to the COVID-19 pandemic, the BATAL project resumed measurements in India. Our observations revealed a complex scenario where the UTLS was influenced by both the ATAL and the transport of aerosols from the Ruang volcanic eruption, which occurred in April 2024. By analyzing data from a suite of instruments, including balloon-borne optical particle counters, backscatter sondes, and aerosol samplers. This analysis will enable us to compare the characteristics of ATAL and volcanic aerosols and discuss the implications of these findings for understanding their combined impact on the atmosphere.
How to cite: Vernier, H., Rastogi, N., Dumelie, N., Vernier, J.-P., Joly, L., Berthet, G., and Meena, R.: Impact of the April 2024 Ruang volcanic eruption on the Asian Tropopause Aerosol Layer: insights from Balloon measurements, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19929, https://doi.org/10.5194/egusphere-egu25-19929, 2025.
"Radiative" or "rapid" adjustments refer to the climate system's responses to an instantaneous radiative forcing, which are independent of surface temperature changes. They occur on timescales from hours to months or even longer, making it difficult to distinguish them from feedbacks. Despite variations in definitions, understanding these processes is essential for advancing climate modeling.
Volcanic eruptions, which introduce scattering aerosol to the stratosphere, serve as natural experiments for studying short-term adjustments. However, the gradual global spread of aerosols during a volcanic eruption complicates analysis. To address this, we took a stepwise approach, starting with idealized model simulations, gradually increasing complexity and finally comparing model results with satellite measurements of the Mt. Pinatubo eruption in 1991. We analyzed data of the abrupt-solm4p experiment from the Cloud Feedback Model Intercomparison Project (CFMIP) within the 6th Coupled Model Intercomparison Project (CMIP6). This experiment simulates a 4% reduction in the solar constant. Additionally, we analyzed an MPI-ESM 1.2 model experiment with both absorbing and non-absorbing stratospheric aerosol layers, using fixed and fully coupled sea surface temperatures. Moreover, results from the volc-pinatubo-full experiment of the CMIP6 Volcanic MIP (VolMIP) were considered, simulating a Pinatubo like eruption, but initializing it from different years of the control run to account for climate variability. Finally, model results were compared to ERA5 reanalysis data of the Pinatubo eruption in 1991.
This study focused on changes in climate variables, cloud properties, and radiative fluxes during the first year after the onset of forcing. All model experiments were initialized on January 1st as the start of forcing, while ERA5 data was used from January 1st, 1992, onwards, since volcanic forcing from the Mt. Pinatubo eruption was strongest at that point.
Results show rapid cooling in the troposphere, especially over Antarctica and the Southern Hemisphere. In contrast, the stratosphere warms significantly when absorbing aerosol is present in the stratopshere. These temperature changes affect the jet streams, as well as the polar night jet, leading to a disruption of the polar vortex and consequently increased surface temperature in the Arctic. Within the first month, the troposphere cools faster than the ocean surface, reducing vertical stability and increasing relative humidity over the ocean. Conversely, over land in the tropics, the opposite effect occurs, influencing land-sea circulation.
How to cite: Lange, C. and Quaas, J.: Rapid adjustments after volcanic eruptions - A stepwise approach towards a better understanding of short-term adjustments in climate models, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20169, https://doi.org/10.5194/egusphere-egu25-20169, 2025.
We ask whether the temperature and precipitation response to large, low-latitude volcanic eruptions is a linear function of the eruption magnitude, as measured by the mass (in Teragrams) of sulfur injected in the lower stratosphere (TgS). Consider the last 2,000 years, magnitudes of climatically interesting eruptions range from roughly 10 TgS from the 1991 Pinatubo and the 1883 Krakatau eruptions, to nearly 30 TgS for the 1815 eruption, to almost 60 TgS for the largest event, the 1257 Samalas eruption. To span this entire range, we simulate eruptions of 5, 10, 20, 40, 80 and 160 TgS, using a state-of-the art climate model with a well-resolved stratosphere. For each eruption magnitude we run a 20-member ensemble of 10-year-long simulations.
We confirm earlier studies, and find that the response is linear up to 20 TgS. However, for eruptions of 40 TgS and above, our analysis reveals a clear nonlinear relationship between eruption magnitude and climate response. We also find important differences between the responses in temperature and precipitation: while the temperature response saturates after 40 TgS, the precipitation response continues to increase in magnitude albeit at a reduced rate. Furthermore, we find that the controlling mechanisms driving the precipitation response are different for the weakest and strongest events. For small eruptions the precipitation anomalies are primarily driven by the cooling surface temperatures (slow response), while for the largest eruptions they are dominated by the absorption of longwave radiation by the volcanic aerosols which warms the lower stratosphere (fast response).
How to cite: Raiter, D., McGraw, Z., and Polvani, L.: Nonlinear precipitation and temperature response to large low-latitude eruptions spanning the last two millennia, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-20342, https://doi.org/10.5194/egusphere-egu25-20342, 2025.
The radiative forcing associated with stratospheric aerosol is often diagnosed using coupled general circulation models. The radiation codes within such models are state-of-the-art, but contain simplifications in order to optimize computational efficiency and make it feasible to perform simulations on climate-relevant time scales. Calculating radiative forcing using different radiative transfer techniques is useful to validate results from GCMs, and explore sensitivities to parameters that are not easily modified in such models. Here, we report on progress toward quantifying global stratospheric aerosol radiative forcing using the SASKTRAN radiative transfer framework, which has a rich heritage in the context of the retrieval of aerosol and gas species from limb scattered radiation. SASKTRAN is coupled to the Easy Volcanic Aerosol (EVA) forcing generator, allowing for realistic but adjustable stratospheric aerosol properties in global or single column radiative transfer calculations. Simulations are used to assess the impact of multiple scattering on the global radiative forcing, and its dependence on location and aerosol perturbation magnitude. We also assess the impact of using the simplified scattering parameters used as input to most GCMs (extinction, single scattering albedo and asymmetry factor) compared to using the full Mie scattering phase function computed from a given aerosol size distribution.
How to cite: Toohey, M., Warnock, T., Zawada, D., and Bourassa, A.: Exploring stratospheric aerosol radiative forcing using the SASKTRAN radiative transfer framework, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-21360, https://doi.org/10.5194/egusphere-egu25-21360, 2025.
