The blue suns of 1831: was the eruption of Ferdinandea, near Sicily, one of the largest volcanic climate forcing events of the nineteenth century?

Abstract. One of the largest climate forcing eruptions of the nineteenth century was, until recently, believed to have taken place at the Babuyan Claro volcano, in the Philippines, in 1831. However, a recent investigation found no reliable evidence of such an eruption, suggesting that the 1831 eruption must have taken place elsewhere. We here present our newly compiled dataset of reported observations of a blue, purple and green sun in August 1831, which we use to reconstruct the transport of a stratospheric aerosol plume from that eruption. The source of the aerosol plume is identified as the eruption of Ferdinandea, which took place about 50 km off the south-west coast of Sicily (37.1∘ N, 12.7∘ E), in July and August 1831. The modest magnitude of this eruption, assigned a volcanic explosivity index (VEI) of 3, has commonly caused it to be discounted or overlooked when identifying the likely source of the stratospheric sulfate aerosol in 1831. It is proposed, however, that convective instability in the troposphere contributed to aerosol reaching the stratosphere and that the aerosol load was enhanced by addition of a sedimentary sulfur component to the volcanic plume. Thus, one of the largest climate forcing volcanic eruptions of the nineteenth century would effectively have been hiding in plain sight, arguably “lowering the bar” for the types of eruptions capable of having a substantial climate forcing impact. Prior estimates of the mass of stratospheric sulfate aerosol responsible for the 1831 Greenland ice core sulfate deposition peaks which have assumed a source eruption at a low-latitude site will, therefore, have been overstated. The example presented in this paper serves as a useful reminder that VEI values were not intended to be reliably correlated with eruption sulfur yields unless supplemented with compositional analyses. It also underlines that eye-witness accounts of historical geophysical events should not be neglected as a source of valuable scientific data.

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The blue suns of 1831: was the eruption of Ferdinandea, near Sicily, one of the largest volcanic climate forcing events of the nineteenth century?

10.5194/cp-2021-78 ◽

2021 ◽

Author(s):

Christopher Garrison ◽

Christopher Kilburn ◽

David Smart ◽

Stephen Edwards

Keyword(s):

Nineteenth Century ◽

Ice Core ◽

Volcanic Eruptions ◽

The Philippines ◽

Stratospheric Aerosol ◽

Scientific Data ◽

Climate Forcing ◽

Volcanic Plume ◽

Sulphate Aerosol ◽

Aerosol Plume

Abstract. One of the largest climate forcing eruptions of the nineteenth century was, until recently, believed to have taken place at Babuyan Claro volcano, in the Philippines, in 1831. However, a recent investigation found no reliable evidence of such an eruption, suggesting that the 1831 eruption must have taken place elsewhere. A newly compiled dataset of reported observations of a blue, purple and green sun in August 1831 is here used to reconstruct the transport of a stratospheric aerosol plume from that eruption. The source of the aerosol plume is identified as the eruption of Ferdinandea, which took place about 50 km off the south-west coast of Sicily (lat. 37.1° N., long. 12.7° E.), in July and August 1831. The modest magnitude of this eruption, assigned a Volcanic Explosivity Index (VEI) of 3, has commonly caused it to be discounted or overlooked when identifying the likely source of the stratospheric sulphate aerosol in 1831. It is proposed, however, that convective instability in the troposphere contributed to aerosol reaching the stratosphere and that the aerosol load was enhanced by addition of a sedimentary sulphur component to the volcanic plume. One of the largest climate forcing volcanic eruptions of the nineteenth century would thus effectively have been hiding in plain sight, arguably ‘lowering the bar’ for the types of eruptions capable of having a substantial climate forcing impact. Prior estimates of the mass of stratospheric sulphate aerosol responsible for the 1831 Greenland ice-core sulphate deposition peaks which have assumed a source eruption at a low-latitude site will therefore have been overstated. The example presented in this paper serves as a useful reminder that VEI values were not intended to be reliably correlated with eruption sulphur yields unless supplemented with compositional analyses. It also underlines that eye-witness accounts of historical geophysical events should not be neglected as a source of valuable scientific data.

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Modelling aspects of the sulfate aerosol evolution after recent volcanic activity

10.5194/egusphere-egu21-16221 ◽

2021 ◽

Author(s):

Christina Brodowsky ◽

Timofei Sukhodolov ◽

Aryeh Feinberg ◽

Michael Höpfner ◽

Thomas Peter ◽

...

Keyword(s):

Volcanic Activity ◽

Climate Model ◽

Volcanic Eruptions ◽

Stratospheric Aerosol ◽

Sulfate Aerosol ◽

Global Climate Models ◽

Volcanic Plume ◽

Free Running ◽

Volcanic Emission ◽

The Impact

Volcanic activity is one of the main natural climate forcings and therefore an accurate representation of volcanic aerosols in global climate models is essential. However, direct modelling of sulfur chemistry, sulfate aerosol microphysics and transport is a complex task involving many uncertainties including those related to the volcanic emission magnitude, vertical shape of the plume, and observations of atmospheric sulfur. This study aims to investigate some of these uncertainties and to analyse the performance of the aerosol-chemistry-climate model SOCOL-AERv2 for three medium-sized volcanic eruptions from Kasatochi in 2008, Sarychev in 2009 and Nabro in 2011. In particular, we investigate the impact of different estimates for the initial volcanic plume height and its SO2 content on the stratospheric aerosol burden. The influence of internal model variability and of modelled dynamics is addressed by three free-running simulations and two nudged simulations at different vertical resolutions. Comparing the modelled evolution of the stratospheric aerosol loading and its spread with the Brewer-Dobson-Circulation (BDC) to satellite measurements reveals in general a very good performance of SOCOL-AERv2 during the considered period. However, the large spread in emission estimates logically leads to significant differences in the modelled aerosol burden. This spread results from both the uncertainty in the total emitted mass of sulfur as well as its vertical distribution relative to the tropopause. An additional source of modelled uncertainty is the tropopause height, which varies among the free-running simulations. Furthermore, the validation is complicated by disagreement between different observational datasets. Nudging effects on the tropospheric clouds were found to affect the tropospheric SO2 oxidation paths and the cross-tropopause transport, leading to increased background burdens both in the troposphere and the stratosphere. This effect can be reduced by nudging only horizontal winds but not temperature. A higher vertical resolution of 90 levels (as opposed to 39 in the standard version) increases the stratospheric residence time of sulfate aerosol after low-latitude eruptions by reducing the diffusion speed out of the tropical reservoir. We conclude that the model's uncertainties can be largely defined by both its set-up as by the volcanic emission parameters.

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Changes in stratospheric aerosol extinction coefficient after the 2018 Ambae eruption as seen by OMPS-LP and ECHAM5-HAM

10.5194/acp-2020-749 ◽

2020 ◽

Author(s):

Elizaveta Malinina ◽

Alexei Rozanov ◽

Ulrike Niemeier ◽

Sandra Peglow ◽

Carlo Arosio ◽

...

Keyword(s):

Extinction Coefficient ◽

Radiative Forcing ◽

Volcanic Eruptions ◽

Stratospheric Aerosol ◽

Retrieval Algorithm ◽

Volcanic Plume ◽

Second Phase ◽

Aerosol Extinction ◽

Aerosol Loading ◽

Aerosol Extinction Coefficient

Abstract. Stratospheric aerosols are an important component of the climate system. They not only change the radiative budget of the Earth but also play an essential role in ozone depletion. Most noticeable those effects are after volcanic eruptions when SO2 injected with the eruption reaches the stratosphere, oxidizes and forms stratospheric aerosol. There have been several studies, where a volcanic eruption plume and the associated radiative forcing were analyzed using climate models. Besides, volcanic eruptions were studied using the data from satellite measurements; however, studies combining both models and measurement data are rare. In this paper, we compared changes in the stratospheric aerosol loading after the 2018 Ambae eruption observed by satellite remote sensing measurements and by a global aerosol model. We use vertical profiles of aerosol extinction coefficient at 869 nm retrieved at IUP Bremen from OMPS-LP (Ozone Mapping and Profiling Suite – Limb Profiler) observations. Here, we present the retrieval algorithm as well as a comparison of the obtained profiles with those from SAGE III/ISS (Stratospheric Aerosol and Gas Experiment III onboard International Space Station). The observed differences are within 25 % for the most latitude bins, which indicates a reasonable quality of the retrieved limb aerosol extinction product. The volcanic plume evolution is investigated using both: monthly mean aerosol extinction coefficients and 10-day averaged data. The measurement results were compared with the model output from ECHAM5-HAM. In order to simulate the eruption accurately, we use SO2 injections estimates from OMPS and OMI for the first phase of eruption and TROPOMI for the second phase. Generally, the agreement between the vertical and geographical distribution of the aerosol extinction coefficient from OMPS-LP and ECHAM is quite remarkable, in particular, for the second phase. We attribute the good consistency between the model and the measurements to the precise estimation of injected SO2 mass and height as well as through nudging to ECMWF reanalysis data. Additionally, we compared the radiative forcing (RF) caused by the increase of the aerosol loading in the stratosphere after the eruption. After accounting for the uncertainties from different RF calculation methods, the RFs from ECHAM and OMPS-LP agree quite well. We estimate the tropical (20° N to 20° S) RF from the second Ambae eruption to be about −0.13 W/m2.

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Impact of the Ambae, Raikoke and Ulawun eruptions in 2018-2019 on the global stratospheric aerosol layer and climate

10.5194/egusphere-egu2020-2406 ◽

2020 ◽

Author(s):

Corinna Kloss ◽

Pasquale Sellitto ◽

Bernard Legras ◽

Jean-Paul Vernier ◽

Fabrice Jégou ◽

...

Keyword(s):

Radiative Transfer ◽

Radiative Forcing ◽

Volcanic Eruptions ◽

Stratospheric Aerosol ◽

Orthogonal Polarization ◽

Transfer Model ◽

Aerosol Layer ◽

The Impact ◽

Aerosol Plume

Using a combination of satellite, ground-based and in-situ observations, and radiative transfer modelling, we quantify the impact of the most recent moderate volcanic eruptions (Ambae, Vanuatu in July 2018; Raikoke, Russia and Ulawun, New Guinea in June 2019) on the global stratospheric aerosol layer and climate.For the Ambae volcano (15&#176;S and 167&#176;E), we use the Stratospheric Aerosol and Gas Experiment III (SAGE III), the Ozone Mapping Profiler Suite (OMPS), the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) and Himawari geostationary satellite observations of the aerosol plume evolution following the Ambae eruption of July 2018. It is shown that the aerosol plume of the main eruption at Ambae in July 2018 was distributed throughout the global stratosphere within the global large-scale circulation (Brewer-Dobson circulation, BDC), to both hemispheres. Ground-based LiDAR observations in Gadanki, India, as well as in-situ Printed Optical Particle Spectrometer (POPS) measurements acquired during the BATAL campaign confirm a widespread perturbation of the stratospheric aerosol layer due to this eruption. Using the UVSPEC radiative transfer model, we also estimate the radiative forcing of this global stratospheric aerosol perturbation. The climate impact is shown to be comparable to that of the well-known and studied recent moderate stratospheric eruptions from Kasatochi (USA, 2008), Sarychev (Russia, 2009) and Nabro (Eritrea, 2011). Top of the atmosphere radiative forcing values between -0.45 and -0.60 W/m2, for the Ambae eruption of July 2018, are found.In a similar manner the dispersion of the aerosol plume of the Raikoke (48&#176;N and 153&#176;E) and Ulawun (5&#176;S and 151&#176;E) eruptions of June 2019 is analyzed. As both of those eruptions had a stratospheric impact and happened almost simultaneously, it is challenging to completely distinguish both events. Even though the eruptions occurred very recently, first results show that the aerosol plume of the Raikoke eruption resulted in an increase in aerosol extinction values, double as high as compared to that of the Ambae eruption. However, as the eruption occurred on higher latitudes, the main bulk of Raikoke aerosols was transported towards the northern higher latitude&#8217;s in the stratosphere within the BDC, as revealed by OMPS, SAGE III and a new detection algorithm for SO2 and sulfate aerosol using IASI (Infrared Atmospheric Sounder Interferometer). Even though the Raikoke eruption had a larger impact on the stratospheric aerosol layer, both events (the eruptions at Raikoke and Ambae) have to be considered in stratospheric aerosol budget and climate studies.

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Equatorward dispersion of high-latitude volcanic plume and its relation to the Asian summer monsoon: a case study of the Sarychev eruption in 2009

10.5194/acp-2017-425 ◽

2017 ◽

Cited By ~ 1

Author(s):

Xue Wu ◽

Sabine Griessbach ◽

Lars Hoffmann

Keyword(s):

High Latitude ◽

Wave Breaking ◽

Emission Rate ◽

Asian Summer Monsoon ◽

Volcanic Eruptions ◽

Stratospheric Aerosol ◽

Volcanic Plume ◽

Aerosol Layer ◽

Subtropical Jet ◽

Asian Summer

Abstract. Tropical volcanic eruptions have been widely studied for their significant contribution to the stratospheric aerosol loading and global climate impacts, but the impact of high-latitude volcanic eruptions on the stratospheric aerosol layer is not clear and the pathway of transporting aerosol from high-latitudes to the tropical stratosphere is not well understood. In this work, we focus on the high-latitude volcano Sarychev (48.1°N, 153.2°E), which erupted during the Asian summer monsoon (ASM) season in 2009, and the influence of ASM on the equatorward dispersion of the volcanic plume. First, the sulfur dioxide (SO2) emission rate and plume height of the Sarychev eruption are estimated with SO2 observations of the Atmospheric Infrared Sounder (AIRS) and a backward trajectory approach, using the Lagrangian particle dispersion model Massive–Parallel Trajectory Calculations (MPTRAC). Then, the transport and dispersion of the plume are simulated using the derived emission rate time series. The transport simulations are compared with SO2 observations from AIRS and validated with aerosol observations from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). The simulations show that about 4% of the emissions were transported to the tropical stratosphere within 50 days after the beginning of the eruption, and the plume dispersed towards the tropical tropopause layer (TTL) through isentropic transport above the subtropical jet. The simulations and MIPAS aerosol data both show that in the vertical range of 360–400 K, the equatorward transport was primarily driven by anticyclonic Rossby wave breaking enhanced by the ASM in boreal summer. The volcanic plume was entrained along the anticyclone flows and reached the TTL as it was transported south-westwards into the deep tropics downstream of the anticyclone. Further, the ASM anticyclone influenced the pathway of aerosols by isolating an aerosol hole inside of the ASM, which was surrounded by aerosol-rich air outside. This transport barrier was best indicated using the potential vorticity gradient approach. Long-term MIPAS aerosol detections show that after entering the TTL, the aerosol from the Sarychev eruption remained in the tropical stratosphere for about 10 months and ascended slowly. The ascent speed agreed well with the ascent speed of water vapour tape recorder. In contrast, by running a hypothetical simulation for a wintertime eruption, it is confirmed that under winter circulations, the equatorward transport of the plume would be suppressed by the strong subtropical jet and weak wave breaking events. In this hypothetic scenario, high-latitude volcanic eruption would not be able to contribute to the tropical stratospheric aerosol layer.

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Volcanic stratospheric sulfur injections and aerosol optical depth during the Holocene (past 11,500 years) from a bipolar ice core array

10.5194/essd-2021-422 ◽

2022 ◽

Author(s):

Michael Sigl ◽

Matthew Toohey ◽

Joseph R. McConnell ◽

Jihong Cole-Dai ◽

Mirko Severi

Keyword(s):

Aerosol Optical Depth ◽

Optical Depth ◽

Ice Core ◽

Ice Cores ◽

Volcanic Eruptions ◽

Stratospheric Aerosol ◽

The Holocene ◽

The Past ◽

New Generation

Abstract. The injection of sulfur into the stratosphere by volcanic eruptions is the dominant driver of natural climate variability on interannual-to-multidecadal timescales. Based on a set of continuous sulfate and sulfur records from a suite of ice cores from Greenland and Antarctica, the HolVol v.1.0 database includes estimates of the magnitudes and approximate source latitudes of major volcanic stratospheric sulfur injection (VSSI) events for the Holocene (from 9500 BCE or 11500 year BP to 1900 CE), constituting an extension of the previous record by 7000 years. The database incorporates new-generation ice-core aerosol records with sub-annual temporal resolution and demonstrated sub-decadal dating accuracy and precision. By tightly aligning and stacking the ice-core records on the WD2014 chronology from Antarctica we resolve long-standing previous inconsistencies in the dating of ancient volcanic eruptions that arise from biased (i.e. dated too old) ice-core chronologies over the Holocene for Greenland. We reconstruct a total of 850 volcanic eruptions with injections in excess of 1 TgS, of which 329 (39 %) are located in the low latitudes with bipolar sulfate deposition, 426 (50 %) are located in the Northern Hemisphere (NH) extratropics and 88 (10 %) are located in the Southern Hemisphere (SH) extratropics. The spatial distribution of reconstructed eruption locations is in agreement with prior reconstructions for the past 2,500 years, and follows the global distribution of landmasses. In total, these eruptions injected 7410 TgS in the stratosphere, for which tropical eruptions accounted for 70 % and NH extratropics for 25 %. A long-term latitudinally and monthly resolved stratospheric aerosol optical depth (SAOD) time series is reconstructed from the HolVol VSSI estimates, representing the first Holocene-scale reconstruction constrained by Greenland and Antarctica ice cores. These new long-term reconstructions of past VSSI and SAOD variability confirm evidence from regional volcanic eruption chronologies (e.g., from Iceland) in showing that the early Holocene (9500–7000 BCE) experienced a higher number of volcanic eruptions (+16 %) and cumulative VSSI (+86 %) compared to the past 2,500 years. This increase coincides with the rapid retreat of ice sheets during deglaciation, providing context for potential future increases of volcanic activity in regions under projected glacier melting in the 21st century. The reconstructed VSSI and SAOD data are available at https://doi.pangaea.de/10.1594/PANGAEA.928646 (Sigl et al., 2021).

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Climate change modulates the stratospheric volcanic sulfate aerosol lifecycle and radiative forcing from tropical eruptions

Nature Communications ◽

10.1038/s41467-021-24943-7 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Thomas J. Aubry ◽

John Staunton-Sykes ◽

Lauren R. Marshall ◽

Jim Haywood ◽

Nathan Luke Abraham ◽

...

Keyword(s):

Climate Change ◽

Radiative Forcing ◽

Climate Model ◽

Volcanic Eruptions ◽

Stratospheric Aerosol ◽

Sulfate Aerosol ◽

Column Height ◽

Surface Cooling ◽

Eruptive Column ◽

Column Dynamics

AbstractExplosive volcanic eruptions affect climate, but how climate change affects the stratospheric volcanic sulfate aerosol lifecycle and radiative forcing remains unexplored. We combine an eruptive column model with an aerosol-climate model to show that the stratospheric aerosol optical depth perturbation from frequent moderate-magnitude tropical eruptions (e.g. Nabro 2011) will be reduced by 75% in a high-end warming scenario compared to today, a consequence of future tropopause height rise and unchanged eruptive column height. In contrast, global-mean radiative forcing, stratospheric warming and surface cooling from infrequent large-magnitude tropical eruptions (e.g. Mt. Pinatubo 1991) will be exacerbated by 30%, 52 and 15% in the future, respectively. These changes are driven by an aerosol size decrease, mainly caused by the acceleration of the Brewer-Dobson circulation, and an increase in eruptive column height. Quantifying changes in both eruptive column dynamics and aerosol lifecycle is therefore key to assessing the climate response to future eruptions.

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Equatorward dispersion of a high-latitude volcanic plume and its relation to the Asian summer monsoon: a case study of the Sarychev eruption in 2009

Atmospheric Chemistry and Physics ◽

10.5194/acp-17-13439-2017 ◽

2017 ◽

Vol 17 (21) ◽

pp. 13439-13455 ◽

Cited By ~ 18

Author(s):

Xue Wu ◽

Sabine Griessbach ◽

Lars Hoffmann

Keyword(s):

High Latitude ◽

Wave Breaking ◽

Asian Summer Monsoon ◽

Volcanic Eruptions ◽

Stratospheric Aerosol ◽

Volcanic Plume ◽

Aerosol Layer ◽

So2 Emission ◽

Subtropical Jet ◽

Asian Summer

Abstract. Tropical volcanic eruptions have been widely studied for their significant contribution to stratospheric aerosol loading and global climate impacts, but the impact of high-latitude volcanic eruptions on the stratospheric aerosol layer is not clear and the pathway of transporting aerosol from high latitudes to the tropical stratosphere is not well understood. In this work, we focus on the high-latitude volcano Sarychev (48.1° N, 153.2° E), which erupted in June 2009, and the influence of the Asian summer monsoon (ASM) on the equatorward dispersion of the volcanic plume. First, the sulfur dioxide (SO2) emission time series and plume height of the Sarychev eruption are estimated with SO2 observations of the Atmospheric Infrared Sounder (AIRS) and a backward trajectory approach using the Lagrangian particle dispersion model Massive–Parallel Trajectory Calculations (MPTRAC). Then, the transport and dispersion of the plume are simulated using the derived SO2 emission time series. The transport simulations are compared with SO2 observations from AIRS and validated with aerosol observations from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). The MPTRAC simulations show that about 4 % of the sulfur emissions were transported to the tropical stratosphere within 50 days after the beginning of the eruption, and the plume dispersed towards the tropical tropopause layer (TTL) through isentropic transport above the subtropical jet. The MPTRAC simulations and MIPAS aerosol data both show that between the potential temperature levels of 360 and 400 K, the equatorward transport was primarily driven by anticyclonic Rossby wave breaking enhanced by the ASM in boreal summer. The volcanic plume was entrained along the anticyclone flows and reached the TTL as it was transported southwestwards into the deep tropics downstream of the anticyclone. Further, the ASM anticyclone influenced the pathway of aerosols by isolating an aerosol hole inside of the ASM, which was surrounded by aerosol-rich air outside. This transport barrier was best indicated using the potential vorticity gradient approach. Long-term MIPAS aerosol detections show that after entering the TTL, aerosol from the Sarychev eruption remained in the tropical stratosphere for about 10 months and ascended slowly. The ascent speed agreed well with the ascent speed of the water vapor tape recorder. Furthermore, a hypothetical MPTRAC simulation for a wintertime eruption was carried out. It is shown that under winter atmospheric circulations, the equatorward transport of the plume would be suppressed by the strong subtropical jet and weak wave breaking events. In this hypothetical scenario, a high-latitude volcanic eruption would not be able to contribute to the tropical stratospheric aerosol layer.

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Detection of an enhanced stratospheric aerosol layer above Europe one year after the eruption of the volcano Raikoke

10.5194/egusphere-egu21-14197 ◽

2021 ◽

Author(s):

Laura Tomsche ◽

Andreas Marsing ◽

Tina Jurkat-Witschas ◽

Johannes Lucke ◽

Katharina Kaiser ◽

...

Keyword(s):

Mass Spectrometer ◽

Lower Stratosphere ◽

Volcanic Eruptions ◽

Stratospheric Aerosol ◽

Sulfate Aerosol ◽

Aerosol Layer ◽

Volcanic Aerosol ◽

Aerosol Mass Spectrometer ◽

Aerosol Mass

Extreme volcanic eruptions inject significant amounts of sulfur-containing species into the lower stratosphere and sustain the stratospheric aerosol layer which tends to cool the atmosphere and surface temperatures.During the BLUESKY campaign in May/June 2020, the aerosol composition and its precursor gas SO2 were measured with a time-of-flight aerosol mass spectrometer onboard the research aircraft HALO and with a atmospheric chemical ionization mass spectrometer onboard the DLR Falcon. While SO2 was slightly above background levels in the lower stratosphere above Europe, the aerosol mass spectrometer detected an extended aerosol layer. This sulfate aerosol layer was observed on most of the HALO flights and the sulfate mixing ratio increased significantly between 10 and 14 km altitude. Back trajectory calculations show no recent transport of polluted boundary layer air or ground-based emissions into the lower stratosphere. Therefore, we suggest that the stratospheric sulfate aerosol layer might be attributed to the aged stratospheric plume of the volcano Raikoke in Japan. In June 2019, Raikoke injected huge amounts of SO2 into the lower stratosphere, which were converted to sulfate and contributed to the stratospheric aerosol layer. This decaying volcanic aerosol layer was observed with the aerosol mass spectrometer over Europe a year after the eruption. The long-term volcanic remnants enhance the total stratospheric aerosol surface area, facilitate heterogeneous reactions on these particles and provide additional cloud condensation nuclei in the UTLS. They further offset some of the reduced sulfur burden from aviation that was observed during the COVID-19 lockdown in 2020. The sensitive and highly time resolved airborne measurements of composition and size of stratospheric aerosol from an explosive volcanic eruption help to better constrain sulfur chemistry in the lower stratosphere, validate satellite observations near their detection threshold and can be used to evaluate dispersion and chemistry-climate models on long-term effects of volcanic aerosol.&#160;

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Impact of a moderate volcanic eruption on chemistry in the lower stratosphere: balloon-borne observations and model calculations

10.5194/acp-2016-763 ◽

2016 ◽

Author(s):

Gwenaël Berthet ◽

Fabrice Jégou ◽

Valéry Catoire ◽

Gisèle Krysztofiak ◽

Jean-Baptiste Renard ◽

...

Keyword(s):

Volcanic Eruption ◽

Lower Stratosphere ◽

Transport Model ◽

Volcanic Eruptions ◽

Measurement Model ◽

Stratospheric Aerosol ◽

Volcanic Plume ◽

Volcanic Aerosol ◽

Model Calculations ◽

Aerosol Loading

Abstract. The major volcanic eruption of Mount Pinatubo in 1991 has been shown to have significant effects on stratospheric chemistry and ozone depletion even at mid-latitudes. Since then, only "moderate" but recurrent volcanic eruptions have modulated the stratospheric aerosol loading such as the eruption of the mid-latitude Sarychev volcano which injected 0.9 Tg of sulfur dioxide (about 20 times less than Pinatubo) in June 2009. In this study, we investigate the chemical impacts of the enhanced liquid sulfate aerosol loading resulting from this moderate eruption using data from a balloon campaign conducted in northern Sweden (Kiruna-Esrange, 67.5° N, 21.0° E) in August-September 2009. Balloon-borne observations of NO2, HNO3 and BrO from infrared and UV-visible spectrometers are compared with the outputs of a three-dimensional (3-D) Chemistry-Transport Model (CTM). It is shown that differences between observations and model outputs are not due to transport calculation issues but rather reflect the chemical impact of the volcanic plume below 19 km in altitude. Good measurement-model agreement is obtained when the CTM is driven by volcanic aerosol loadings derived from in situ or space-borne data. As a result of enhanced N2O5 hydrolysis in the Sarychev volcanic aerosol conditions, the model calculates reductions of ~ 45 % and increases of ~ 11 % in NO2 and HNO3 amounts respectively over the summer 2009 period. The decrease in NOx abundances is limited due to the expected saturation effect for high aerosol loadings. The links between the various chemical catalytic cycles involving chlorine, bromine, nitrogen and HOx compounds in the lower stratosphere are discussed. The increased BrO amounts (~ 22 %) compare rather well with the balloon-borne observations when volcanic aerosol levels are accounted for in the CTM and appear to be mainly controlled by the coupling with nitrogen chemistry rather than by enhanced BrONO2 hydrolysis. Simulated effects of the Sarychev eruption on chlorine activation and partitioning are very limited in the high temperature conditions in the stratosphere at the period considered, inhibiting the effect of ClONO2 hydrolysis. As a consequence, the simulated ozone loss due to the Sarychev aerosols is low with a reduction of 1.1 % of the ozone budget at 16.5 km. Some comparisons with the reported Pinatubo chemical impacts are also provided and overall the Sarychev aerosols have led to less chemical effects than the Pinatubo event.

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