Dispersion Model Evaluation for the Sulfur Dioxide Plume from the 2019 Raikoke Eruption using Satellite Measurements.

2020 ◽  
Author(s):  
Johannes de Leeuw ◽  
Anja Schmidt ◽  
Claire Witham ◽  
Nicolas Theys ◽  
Richard Pope ◽  
...  
Keyword(s):  
Sulfur Dioxide ◽  
Dispersion Model ◽  
European Space Agency ◽  
Volcanic Eruptions ◽  
Numerical Dispersion ◽  
Aviation Industry ◽  
Volcanic Plume ◽  
Satellite Measurements ◽  
Volcanic Gas ◽  
Vertical Column

<p>Volcanic eruptions pose a serious threat to the aviation industry causing widespread disruption. To identify any potential impacts, nine Volcanic Ash Advisory Centres (VAACs) provide global monitoring of all eruptions, informing stakeholders how each volcanic eruption might interfere with aviation. Numerical dispersion models represent a vital infrastructure when assessing and forecasting the atmospheric conditions from a volcanic plume.</p><p>In this study we investigate the 2019 Raikoke eruption, which emitted approximately 1.5 Tg of sulfur dioxide (SO<sub>2</sub>) representing the largest volcanic emission of SO<sub>2</sub> into the stratosphere since the Nabro eruption in 2011. Using the UK Met Office’s Numerical Atmospheric-dispersion Modelling Environment (NAME), we simulate the evolution of the volcanic gas and aerosol particle plumes (SO<sub>2</sub> and sulfate, SO<sub>4</sub>) across the Northern Hemisphere between 21<sup>st</sup> June and 17<sup>th </sup>July. We evaluate the skills and limitations of NAME in terms of modelling volcanic SO<sub>2 </sub>plumes, by comparing our simulations to high-resolution measurements from the Tropospheric Monitoring Instrument (TROPOMI) on-board the European Space Agency (ESA)’s Sentinel 5 – Precursor (S5P) satellite.</p><p>Our comparisons show that NAME accurately simulates the observed location and shape of the SO<sub>2</sub> plume in the first few weeks after the eruption. NAME also reproduces the magnitude of the observed SO<sub>2 </sub>vertical column densities, when emitting 1.5 Tg of SO<sub>2</sub>, during the first 48 hours after the eruption. On longer timescales, we find that the model-simulated SO<sub>2 </sub>plume in NAME is more diffuse than in the TROPOMI measurements, resulting in an underestimation of the peak SO<sub>2</sub> vertical column densities in the model. This suggests that the diffusion parameters used in NAME are too large in the upper troposphere and lower stratosphere.</p><p>Finally, NAME underestimates the total mass of SO<sub>2</sub> when compared to estimates from TROPOMI, however emitting 2 Tg of SO<sub>2</sub> in the model improves the comparison, resulting in very good agreement with the satellite measurements.</p>

scholarly journals Determination of time- and height-resolved volcanic ash emissions and their use for quantitative ash dispersion modeling: the 2010 Eyjafjallajökull eruption

2011 ◽  
Vol 11 (9) ◽  
pp. 4333-4351 ◽  
Author(s):  
A. Stohl ◽  
A. J. Prata ◽  
S. Eckhardt ◽  
L. Clarisse ◽  
A. Durant ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Dispersion Model ◽  
A Priori ◽  
Volcanic Eruptions ◽  
General Nature ◽  
Aviation Industry ◽  
Dispersion Modeling ◽  
Source Information ◽  
European Area ◽  
Ash Dispersion

Abstract. The April–May, 2010 volcanic eruptions of Eyjafjallajökull, Iceland caused significant economic and social disruption in Europe whilst state of the art measurements and ash dispersion forecasts were heavily criticized by the aviation industry. Here we demonstrate for the first time that large improvements can be made in quantitative predictions of the fate of volcanic ash emissions, by using an inversion scheme that couples a priori source information and the output of a Lagrangian dispersion model with satellite data to estimate the volcanic ash source strength as a function of altitude and time. From the inversion, we obtain a total fine ash emission of the eruption of 8.3 ± 4.2 Tg for particles in the size range of 2.8–28 μm diameter. We evaluate the results of our model results with a posteriori ash emissions using independent ground-based, airborne and space-borne measurements both in case studies and statistically. Subsequently, we estimate the area over Europe affected by volcanic ash above certain concentration thresholds relevant for the aviation industry. We find that during three episodes in April and May, volcanic ash concentrations at some altitude in the atmosphere exceeded the limits for the "Normal" flying zone in up to 14 % (6–16 %), 2 % (1–3 %) and 7 % (4–11 %), respectively, of the European area. For a limit of 2 mg m−3 only two episodes with fractions of 1.5 % (0.2–2.8 %) and 0.9 % (0.1–1.6 %) occurred, while the current "No-Fly" zone criterion of 4 mg m−3 was rarely exceeded. Our results have important ramifications for determining air space closures and for real-time quantitative estimations of ash concentrations. Furthermore, the general nature of our method yields better constraints on the distribution and fate of volcanic ash in the Earth system.

scholarly journals A new discrete wavelength BUV algorithm for consistent volcanic SO<sub>2</sub> retrievals from multiple satellite missions

2019 ◽  
Author(s):  
Bradford L. Fisher ◽  
Nickolay A. Krotkov ◽  
Pawan K. Bhartia ◽  
Can Li ◽  
Simon Carn ◽  
...  
Keyword(s):  
Sulfur Dioxide ◽  
Principal Component ◽  
Volcanic Eruptions ◽  
Climate Data ◽  
Ozone Monitoring Instrument ◽  
Vertical Column ◽  
Earth Observing System ◽  
Paper Supplement ◽  
Process Measurements ◽  
Pca Algorithm

Abstract. This paper describes a new discrete wavelength algorithm developed for retrieving volcanic sulfur dioxide (SO2) vertical column density (VCD) from UV observing satellites. The Multi-Satellite SO2 algorithm (MS_SO2) simultaneously retrieves column densities of sulfur dioxide, ozone, Lambertian Effective Reflectivity (LER) and its spectral dependence. It is used operationally to process measurements from the heritage Total Ozone Mapping Spectrometer (TOMS) on board NASA's Nimbus-7 satellite (N7/TOMS: 1978–1993) and from the current Earth Polychromatic Imaging Camera (EPIC) on board Deep Space Climate Observatory (DSCOVR: 2015–) from the Earth-Sun Lagrange (L1) orbit. Results from MS_SO2 algorithm for several volcanic cases were validated using the more sensitive principal component analysis (PCA) algorithm. The PCA is an operational algorithm used by NASA to retrieve SO2 from hyperspectral UV spectrometers, such as Ozone Monitoring Instrument (OMI) on board NASA’s Earth Observing System Aura satellite and Ozone Mapping and Profiling Suite (OMPS) on board NASA-NOAA Suomi National Polar Partnership (S-NPP) satellite. For this comparative study, the PCA algorithm was modified to use the discrete wavelengths of the Nimbus7/TOMS instrument, described in S1 of the paper supplement. Our results demonstrate good agreement between the two retrievals for the largest volcanic eruptions of the satellite era, such as 1991 Pinatubo eruption. To estimate SO2 retrieval uncertainties we use radiative transfer simulations explicitly accounting for volcanic sulfate and ash aerosols. Our results suggest that the discrete-wavelength MS_SO2 algorithm, although less sensitive than hyperspectral PCA algorithm, can be adapted to retrieve volcanic SO2 VCDs from contemporary hyperspectral UV instruments, such as OMI and OMPS, to create consistent, multi-satellite, long-term volcanic SO2 climate data records.

Ground-based and satellite measurements of the SO2 plume from the eruption of Raikoke volcano in June 2019

2020 ◽  
Author(s):  
Vitali Fioletov ◽  
Chris Sioris ◽  
Xiaoyi Zhao ◽  
Debora Griffin ◽  
Chris McLinden ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Western Hemisphere ◽  
Lagrangian Model ◽  
Volcanic Plume ◽  
Back Trajectory ◽  
High Latitudes ◽  
Ozone Monitoring Instrument ◽  
Satellite Measurements ◽  
Vertical Column ◽  
Monitoring Instrument

&lt;p&gt;The eruption of the Raikoke volcano (Kuril Islands) on June 21-22, 2019, created a large plume of sulfur dioxide (SO&lt;sub&gt;2&lt;/sub&gt;) that reached the upper troposphere and lower stratosphere. The plume persisted in the atmosphere over the middle and high latitudes of the Western Hemisphere for more than a month creating a rare validation opportunity with multiple collocated measurements from ground and space both revealing enhanced SO&lt;sub&gt;2&lt;/sub&gt; vertical column densities (VCDs). Moreover, since the plume was often located over high latitudes, multiple orbits per day from the polar orbiting satellites could be utilized. Pandora sunphotometer measurements at Edmonton and Eureka, Canada, and at Fairbanks, Alaska, and Brewer spectrophotometer measurements at seven Canadian sites (Saturna, Edmonton, Churchill, Resolute, Eureka, and Alert) reported SO&lt;sub&gt;2&lt;/sub&gt; values up to 15 Dobson Units (DU, where 1 DU = 2.69 &amp;#215; 10&lt;sup&gt;16&lt;/sup&gt; molecules/cm&amp;#178;). These measurements were compared with satellite SO&lt;sub&gt;2&lt;/sub&gt; VCDs obtained by the Sentinel 5p TROPOspheric Monitoring Instrument (TROPOMI), AURA Ozone Monitoring Instrument (OMI), and Suomi NPP Ozone Mapping Profiling Suite (OMPS). Back-trajectory Lagrangian model analysis and satellite SO&lt;sub&gt;2&lt;/sub&gt; profile measurements by the Atmospheric Chemistry Experiment mission Fourier transform spectrometer (ACE/FTS) on board the Canadian satellite SCISAT demonstrated that the volcanic plume was located at 8-25 km. In general, ground-based and satellite measurements show a very good agreement. However, the exact ground-based and satellite viewing geometry should be considered when such measurements are taken near the edge of the plume.&lt;/p&gt;

scholarly journals Characterization of a volcanic ash episode in southern Finland caused by the Grimsvötn eruption in Iceland in May 2011

2011 ◽  
Vol 11 (9) ◽  
pp. 24933-24968 ◽  
Author(s):  
V.-M. Kerminen ◽  
J. V. Niemi ◽  
H. Timonen ◽  
M. Aurela ◽  
A. Frey ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Dispersion Model ◽  
Volcanic Eruptions ◽  
Particle Analysis ◽  
Satellite Measurements ◽  
Volcanic Origin ◽  
Model Simulations ◽  
Volcanic Material ◽  
Micron Particle ◽  
Mass Concentrations

Abstract. The volcanic eruption of Grimsvötn in Iceland in May 2011, affected surface-layer air quality at several locations in Northern Europe. In Helsinki, Finland, the main pollution episode lasted for more than 8 h around the noon of 25 May. We characterized this episode by relying on detailed physical, chemical and optical aerosol measurements. The analysis was aided by air mass trajectory calculations, satellite measurements, and dispersion model simulations. During the episode, volcanic ash particles were present at sizes from less than 0.5 μm up to sizes >10 μm. The mass mean diameter of ash particles was a few μm in the Helsinki area, and the ash enhanced PM10 mass concentrations up to several tens of μg m−3. Individual particle analysis showed that some ash particles appeared almost non-reacted during the atmospheric transportation, while most of them were mixed with sea salt or other type of particulate matter. Also sulfate of volcanic origin appeared to have been transported to our measurement site, but its contribution to the aerosol mass was minor due the separation of ash-particle and sulfur dioxide plumes shortly after the eruption. The volcanic material had very little effect on PM1 mass concentrations or sub-micron particle number size distributions in the Helsinki area. The aerosol scattering coefficient was increased and visibility was slightly decreased during the episode, but in general changes in aerosol optical properties due to volcanic aerosols seem to be difficult to be distinguished from those induced by other pollutants present in a continental boundary layer. The case investigated here demonstrates clearly the power of combining surface aerosol measurements, dispersion model simulations and satellite measurements in analyzing surface air pollution episodes caused by volcanic eruptions. None of these three approaches alone would be sufficient to forecast, or even to unambiguously identify, such episodes.

scholarly journals Space based observation of volcanic iodine monoxide

2016 ◽  
Author(s):  
Anja Schönhardt ◽  
Andreas Richter ◽  
Nicolas Theys ◽  
John P. Burrows
Keyword(s):  
Spatial Distribution ◽  
Volcanic Eruptions ◽  
Observational Evidence ◽  
Volcanic Plume ◽  
Satellite Measurements ◽  
Volcanic Plumes ◽  
Iodine Monoxide ◽  
Order Of Magnitude ◽  
Iodine Oxides ◽  
Major Eruption

Abstract. Volcanic eruptions inject substantial amounts of halogens into the atmosphere. Chlorine and bromine oxides have frequently been observed in volcanic plumes from different instrumental platforms, from ground, aircraft as well as from satellite. The present study is the first observational evidence that iodine oxides are also emitted into the atmosphere during volcanic eruptions. Large column amounts of iodine monoxide, IO, have been observed in satellite measurements following the major eruption of the Kasatochi volcano, Alaska, in 2008. The IO signal is detected in measurements made both by SCIAMACHY on ENVISAT and GOME-2 on MetOp-A. Following the eruption on August 07, 2008, strongly elevated levels of IO slant columns of more than 4 × 1013 molec/cm2 are retrieved along the volcanic plume trajectories for several days. The retrieved IO columns from the different instruments are consistent and the spatial distribution of the IO plume is similar to that of BrO. Details in the spatial distribution, however, differ between IO, BrO and sulphur dioxide, SO2. The columns of IO are approximately one order of magnitude smaller than those of BrO. Using the GOME-2A observations, the total mass of IO in the volcanic plume injected into the atmosphere from the eruption of Kasatochi on August 07, 2008, is determined to be on the order of 10 Mg.

scholarly journals Space-based observation of volcanic iodine monoxide

2017 ◽  
Vol 17 (7) ◽  
pp. 4857-4870 ◽  
Author(s):  
Anja Schönhardt ◽  
Andreas Richter ◽  
Nicolas Theys ◽  
John P. Burrows
Keyword(s):  
Spatial Distribution ◽  
Volcanic Eruptions ◽  
Volcanic Plume ◽  
Satellite Measurements ◽  
Volcanic Plumes ◽  
Iodine Monoxide ◽  
Order Of Magnitude ◽  
Scanning Imaging ◽  
Iodine Oxides ◽  
Major Eruption

Abstract. Volcanic eruptions inject substantial amounts of halogens into the atmosphere. Chlorine and bromine oxides have frequently been observed in volcanic plumes from different instrumental platforms such as from ground, aircraft and satellites. The present study is the first observational evidence that iodine oxides are also emitted into the atmosphere during volcanic eruptions. Large column amounts of iodine monoxide, IO, are observed in satellite measurements following the major eruption of the Kasatochi volcano, Alaska, in 2008. The IO signal is detected in measurements made both by SCIAMACHY (Scanning Imaging Absorption Spectrometer for Atmospheric CHartographY) on ENVISAT (Environmental Satellite) and GOME-2 (Global Ozone Monitoring Experiment-2) on MetOp-A (Meteorological Operational Satellite A). Following the eruption on 7 August 2008, strongly elevated levels of IO slant columns of more than 4 × 1013 molec cm−2 are retrieved along the volcanic plume trajectories for several days. The retrieved IO columns from the different instruments are consistent, and the spatial distribution of the IO plume is similar to that of bromine monoxide, BrO. Details in the spatial distribution, however, differ between IO, BrO and sulfur dioxide, SO2. The column amounts of IO are approximately 1 order of magnitude smaller than those of BrO. Using the GOME-2A observations, the total mass of IO in the volcanic plume injected into the atmosphere from the eruption of Kasatochi on 7 August 2008, is determined to be on the order of 10 Mg.

scholarly journals Characterization of a volcanic ash episode in southern Finland caused by the Grimsvötn eruption in Iceland in May 2011

2011 ◽  
Vol 11 (23) ◽  
pp. 12227-12239 ◽  
Author(s):  
V.-M. Kerminen ◽  
J. V. Niemi ◽  
H. Timonen ◽  
M. Aurela ◽  
A. Frey ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Dispersion Model ◽  
Volcanic Eruptions ◽  
Particle Analysis ◽  
Satellite Measurements ◽  
Volcanic Origin ◽  
Model Simulations ◽  
Volcanic Material ◽  
Micron Particle ◽  
Mass Concentrations

Abstract. The volcanic eruption of Grimsvötn in Iceland in May 2011 affected surface-layer air quality at several locations in Northern Europe. In Helsinki, Finland, the main pollution episode lasted for more than 8 h around the noon of 25 May. We characterized this episode by relying on detailed physical, chemical and optical aerosol measurements. The analysis was aided by air mass trajectory calculations, satellite measurements, and dispersion model simulations. During the episode, volcanic ash particles were present at sizes from less than 0.5 μm up to sizes >10 μm. The mass mean diameter of ash particles was a few μm in the Helsinki area, and the ash enhanced PM10 mass concentrations up to several tens of μg m−3. Individual particle analysis showed that some ash particles appeared almost non-reacted during the atmospheric transportation, while most of them were mixed with sea salt or other type of particulate matter. Also sulfate of volcanic origin appeared to have been transported to our measurement site, but its contribution to the aerosol mass was minor due the separation of ash-particle and sulfur dioxide plumes shortly after the eruption. The volcanic material had very little effect on PM1 mass concentrations or sub-micron particle number size distributions in the Helsinki area. The aerosol scattering coefficient was increased and visibility was slightly decreased during the episode, but in general changes in aerosol optical properties due to volcanic aerosols seem to be difficult to be distinguished from those induced by other pollutants present in a continental boundary layer. The case investigated here demonstrates clearly the power of combining surface aerosol measurements, dispersion model simulations and satellite measurements in analyzing surface air pollution episodes caused by volcanic eruptions. None of these three approaches alone would be sufficient to forecast, or even to unambiguously identify, such episodes.

scholarly journals Determination of time- and height-resolved volcanic ash emissions for quantitative ash dispersion modeling: the 2010 Eyjafjallajökull eruption

2011 ◽  
Vol 11 (2) ◽  
pp. 5541-5588 ◽  
Author(s):  
A. Stohl ◽  
A. J. Prata ◽  
S. Eckhardt ◽  
L. Clarisse ◽  
A. Durant ◽  
...  
Keyword(s):  
Volcanic Ash ◽  
Size Range ◽  
Dispersion Model ◽  
A Priori ◽  
Volcanic Eruptions ◽  
General Nature ◽  
Aviation Industry ◽  
Dispersion Modeling ◽  
Source Information ◽  
Ash Dispersion

Abstract. The April–May 2010 volcanic eruptions of Eyjafjallajökull, Iceland caused significant economic and social disruption in Europe whilst state of the art measurements and ash dispersion forecasts were heavily criticized by the aviation industry. Here we demonstrate for the first time that dramatic improvements can be made in quantitative predictions of the fate of volcanic ash emissions, by using an inversion scheme that couples a priori source information and the output of a Lagrangian dispersion model with satellite data to estimate the volcanic ash source strength as a function of altitude and time. From the inversion, we obtain a total fine ash emission of the eruption of 8.3 ± 4.2 Tg for particles in the size range of 2.8–28 μm diameter and extrapolate this to a total ash emission of 11.9 ± 5.9 Tg for the size range of 0.25–250 μm. We evaluate the results of our a posteriori model using independent ground-based, airborne and space-borne measurements both in case studies and statistically. Subsequently, we estimate the area over Europe affected by volcanic ash above certain concentration thresholds relevant for the aviation industry. We find that during three episodes in April and May, volcanic ash concentrations at some altitude in the atmosphere exceeded the limits for the "normal" flying zone in up to 14% (6–16%), 2% (1–3%) and 7% (4–11%), respectively, of the European area. For a limit of 2 mg m−3 only two episodes with fractions of 1.5% (0.2–2.8%) and 0.9% (0.1–1.6%) occurred, while the current "no-fly" zone criterion of 4 mg m−3 was rarely exceeded. Our results have important ramifications for determining air space closures and for real-time quantitative estimations of ash concentrations. Furthermore, the general nature of our method yields better constraints on the distribution and fate of volcanic ash in the Earth system.

scholarly journals Volcanic SO<sub>2</sub> Layer Height by TROPOMI/S5P; validation against IASI/MetOp and CALIOP/CALIPSO observations

2021 ◽  
Author(s):  
Maria-Elissavet Koukouli ◽  
Konstantinos Michailidis ◽  
Pascal Hedelt ◽  
Isabelle A. Taylor ◽  
Antje Inness ◽  
...  
Keyword(s):  
Real Time ◽  
Traffic Safety ◽  
European Space Agency ◽  
Volcanic Eruptions ◽  
Mean Difference ◽  
Atmospheric Composition ◽  
Retrieval Algorithm ◽  
Volcanic Plume ◽  
Layer Height ◽  
The Impact

Abstract. Volcanic eruptions eject large amounts of ash and trace gases such as sulphur dioxide (SO2) into the atmosphere. A significant difficulty in mitigating the impact of volcanic SO2 clouds on air traffic safety is that these gas emissions can be rapidly transported over long distances. The use of space-borne instruments enables the global monitoring of volcanic SO2 emissions in an economical and risk-free manner. Within the European Space Agency (ESA) Sentinel-5p+ Innovation project, the S5P SO2 Layer Height (S5P+I: SO2 LH) activities led to the improvements on the retrieval algorithm and generation of the corresponding near-real-time S5P SO2 LH products. These are currently operationally provided, in near-real-time, by the German Aerospace Center (DLR) in the framework of the Innovative Products for Analyses of Atmospheric Composition, INPULS, project. The main aim of this paper is to present its extensive verification, accomplished within the S5P+I: SO2 LH project, over major recent volcanic eruptions, against collocated space-born measurements from the IASI/Metop and CALIOP/CALIPSO instruments, as well as assess its impact on the forecasts provided by the Copernicus Atmospheric Monitoring Service, CAMS. The mean difference between S5P and IASI observations for the Raikoke 2019, the Nishinoshima 2020 and the La Soufrière-St Vincent, 2021 eruptive periods is ~0.5 ± 3 km, while for the Taal 2020 eruption, a larger difference was found, between 3 and 4 ± 3 km. The comparison of the daily mean SO2 layer heights further demonstrates the capabilities of this near-real-time product, with slopes between 0.8 and 1 and correlations ranging between 0.6 and 0.8. Comparisons between the S5P+I: SO2 LH and the CALIOP/CALIPSO ash plume height are also satisfactory at −2.5 ± 2 km, considering that the injected SO2 and ash plumes’ locations do not always coincide over an eruption. Furthermore, the CAMS assimilation of the S5P+I: SO2 LH product led to much improved model output against the non-assimilated IASI layer heights, with a mean difference of 1.5 ± 2 km compared to the original CAMS analysis, and improved the geographical spread of the Raikoke volcanic plume following the eruptive days.

scholarly journals A new discrete wavelength backscattered ultraviolet algorithm for consistent volcanic SO<sub>2</sub> retrievals from multiple satellite missions

2019 ◽  
Vol 12 (9) ◽  
pp. 5137-5153
Author(s):  
Bradford L. Fisher ◽  
Nickolay A. Krotkov ◽  
Pawan K. Bhartia ◽  
Can Li ◽  
Simon A. Carn ◽  
...  
Keyword(s):  
Sulfur Dioxide ◽  
Principal Component ◽  
Volcanic Eruptions ◽  
Climate Data ◽  
Ozone Monitoring Instrument ◽  
Vertical Column ◽  
Earth Observing System ◽  
Vertical Column Density ◽  
Process Measurements ◽  
Pca Algorithm

Abstract. This paper describes a new discrete wavelength algorithm developed for retrieving volcanic sulfur dioxide (SO2) vertical column density (VCD) from UV observing satellites. The Multi-Satellite SO2 algorithm (MS_SO2) simultaneously retrieves column densities of sulfur dioxide, ozone, and Lambertian effective reflectivity (LER) and its spectral dependence. It is used operationally to process measurements from the heritage Total Ozone Mapping Spectrometer (TOMS) onboard NASA's Nimbus-7 satellite (N7/TOMS: 1978–1993) and from the current Earth Polychromatic Imaging Camera (EPIC) onboard Deep Space Climate Observatory (DSCOVR: 2015–ongoing) from the Earth–Sun Lagrange (L1) orbit. Results from MS_SO2 algorithm for several volcanic cases were assessed using the more sensitive principal component analysis (PCA) algorithm. The PCA is an operational algorithm used by NASA to retrieve SO2 from hyperspectral UV spectrometers, such as the Ozone Monitoring Instrument (OMI) onboard NASA's Earth Observing System Aura satellite and Ozone Mapping and Profiling Suite (OMPS) onboard NASA–NOAA Suomi National Polar Partnership (SNPP) satellite. For this comparative study, the PCA algorithm was modified to use the discrete wavelengths of the Nimbus-7/TOMS instrument, described in Sect. S1 of the Supplement. Our results demonstrate good agreement between the two retrievals for the largest volcanic eruptions of the satellite era, such as the 1991 Pinatubo eruption. To estimate SO2 retrieval systematic uncertainties, we use radiative transfer simulations explicitly accounting for volcanic sulfate and ash aerosols. Our results suggest that the discrete-wavelength MS_SO2 algorithm, although less sensitive than hyperspectral PCA algorithm, can be adapted to retrieve volcanic SO2 VCDs from contemporary hyperspectral UV instruments, such as OMI and OMPS, to create consistent, multi-satellite, long-term volcanic SO2 climate data records.

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