Atmospheric processes affecting the separation of volcanic ash and SO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; in volcanic eruptions: inferences from the May 2011 Grímsvötn eruption

Prata, Fred; Woodhouse, Mark; Huppert, Herbert E.; Prata, Andrew; Thordarson, T.; Carn, S. A.

doi:10.5194/acp-17-10709-2017

Cited by 50 publications

(43 citation statements)

References 81 publications

(112 reference statements)

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“…This is also reflected in the ashfall deposition values, as a background value of ∼ 1-10 g m −2 mo −1 was also seen independently of the season and dominant wind patterns. Separation of SO 2 and volcanic ash is known to occur depending on the volcanological and meteorological conditions during an eruption (Prata et al, 2017). Even though previous studies focusing on volcanic emissions from Sakurajima have noted a high correlation between the concentrations of SO 2 and SPM after large eruptions Hillman et al, 2012;Sakamoto and Kinoshita, 2015), evidence shown here suggest that this correlation is weaker for long-term dispersal and holds true mainly for stations close to the volcano.…”

Section: Discussioncontrasting

confidence: 45%

Statistical analysis of dispersal and deposition patterns of volcanic emissions from Mt. Sakurajima, Japan

Poulidis

Takemi

Shimizu

et al. 2018

Atmospheric Environment

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A B S T R A C TWith the eruption of Eyjafjallajökull (Iceland) in 2010, interest in the transport of volcanic ash after moderate to major eruptions has increased with regards to both the physical and the emergency hazard management aspects. However, there remain significant gaps in the understanding of the long-term behaviour of emissions from volcanoes with long periods of activity. Mt. Sakurajima (Japan) provides us with a rare opportunity to study such activity, due to its eruptive behaviour and dense observation network. In the 6-year period from 2009 to 2015, the volcano was erupting at an almost constant rate introducing approximately 500 kt of ash per month to the atmosphere. The long-term characteristics of the transport and deposition of ash and SO 2 in the area surrounding the volcano are studied here using daily surface observations of suspended particulate matter (SPM) and SO 2 and monthly ashfall values.Results reveal different dispersal patterns for SO 2 and volcanic ash, suggesting volcanic emissions' separation in the long-term. Peak SO 2 concentrations at different locations on the volcano vary up to 2 orders of magnitude and decrease steeply with distance. Airborne volcanic ash increases SPM concentrations uniformly across the area surrounding the volcano, with distance from the vent having a secondary effect. During the period studied here, the influence of volcanic emissions was identifiable both in SO 2 and SPM concentrations which were, at times, over the recommended exposure limits defined by the Japanese government, European Union and the World Health Organisation.Depositional patterns of volcanic ash exhibit elements of seasonality, consistent with previous studies. Climatological and topographic effects are suspected to impact the deposition of volcanic ash away from the vent: for sampling stations located close to complex topographical elements, sharp changes in the deposition patterns were observed, with ash deposits for neighbouring stations as close as 5 km differing as much as an order of magnitude. Despite these effects, deposition was sufficiently approximated by an inverse power law relationship, the fidelity of which depended on the distance from the vent: for proximal to intermediate areas (20 km), errors decrease with longer accumulation periods (tested here for 1-72 months), while the opposite was seen for deposition in distal areas (>20 km).

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Section: Discussioncontrasting

confidence: 45%

Statistical analysis of dispersal and deposition patterns of volcanic emissions from Mt. Sakurajima, Japan

Poulidis

Takemi

Shimizu

et al. 2018

Atmospheric Environment

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“…This study addresses the three Icelandic volcanoes that were active during the 19-year period covered by the NASA Earth Observing System (EOS) to date. Detailed discussion of the individual eruptions have previously been published for: Eyjafjallajökull 2010 (e.g., Arason et al, 2011;Cioni et al, 2014;Gudmundsson et al, 2012;Kahn & Limbacher, 2012;Sigmarsson et al, 2011;Sigmundsson et al, 2010), Grímsvötn 2011 (Moxnes et al, 2014;Petersen et al, 2012;Prata et al, 2017), and Holuhraun 2014-2015 • Remote sensing observations of Icelandic eruptions distinguish different types of volcanic emissions • Evidence of downwind aerosol formation, particle hydration, and possible activation were identified in Icelandic plumes • Variations in derived particle proxies in ash-rich plumes correlate with changes in eruptive processes and magma composition Supporting Information:…”

Section: Introductionmentioning

confidence: 99%

The Evolution of Icelandic Volcano Emissions, as Observed From Space in the Era of NASA's Earth Observing System (EOS)

Flower

Kahn

2020

JGR Atmospheres

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Volcanoes are natural phenomena that have global environmental impacts. Satellite remote sensing can help classify volcanic eruptions and track the dispersion of emissions. We assess multiple volcanic eruptions in Iceland (Eyjafjallajökull 2010, Grímsvötn 2011, and Holuhraun 2014-2015), using space-borne observations to infer information about the geological dynamics of each volcano and the properties and evolution of plume particles. We derive qualitative constraints on plume particle size, shape, and light-absorption characteristics from Multiangle Imaging SpectroRadiometer (MISR) space-borne imagery. With the MISR Research Algorithm (RA), we distinguish sulfate/water-dominated volcanic plumes from Holuhraun and ash-dominated plumes from Eyjafjallajökull and Grímsvötn, and even identify subtler changes in ash particle size and light-absorption within plumes. Additionally, plume heights are retrieved geometrically from MISR. These are combined with surface thermal anomalies from the MODerate resolution Imaging Spectroradiometer (MODIS) and SO 2 concentrations derived from the Ozone Monitoring Instrument (OMI) to synthesize eruption remote-sensing chronologies. Signals related to differences in particle properties are identified and linked to evolving magma composition at Eyjafjallajökull. The results illustrate the potential to distinguish qualitative differences in eruptive magma composition based on particle light absorption and plume profile from remote-sensing. For the sulfate-rich Holuhraun plumes, the influence of aerosol hygroscopic growth during transport is inferred from such data. Three processes appear to dominate plume evolution in Iceland: downwind aerosol formation, particle hydration, and particle deposition. This work demonstrates enhanced MISR capabilities and, more generally, remote-sensing analysis that can be applied globally, especially where suborbital volcano observations are limited or entirely absent.

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“…As this ice-rich region evolved, the ash-rich portion of the cloud drifted westwards, with a clear separation of the two parts of the eruption cloud. Separation of constituents in eruption clouds has been noticed and discussed previously [71] in the context of ash and SO 2 gas separation for the May 2011 eruption of Grímsvötn in Iceland. Ice and ash separation has not been previously reported in the literature.…”

Section: Volcanic Icementioning

confidence: 82%

“…The case study for the volcanogenic ice and ash from the eruption of Sinabung, Indonesia illustrates a new feature of complex mixed-constituent volcanic clouds: separation of ice-rich and ash-rich portions of the eruption clouds. Previous work [71,83] has shown that volcanic SO 2 and ash can travel together or undergo maximum separation, and separation of ice and ash clouds in the 2005 Manam eruption can be seen in [63] but the process is not elaborated. The separation of ice-rich and ash-rich portions of volcanic clouds and indeed of SO 2 -rich portions, has important consequences for dispersion modelling and forecasting volcanic hazards to aviation.…”

Section: Discussionmentioning

confidence: 99%

Passive Earth Observations of Volcanic Clouds in the Atmosphere

Prata

Lynch

2019

Atmosphere

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Current Earth Observation (EO) satellites provide excellent spatial, temporal and spectral coverage for passive measurements of atmospheric volcanic emissions. Of particular value for ash detection and quantification are the geostationary satellites that now carry multispectral imagers. These instruments have multiple spectral channels spanning the visible to infrared (IR) wavelengths and provide 1 × 1 km2 to 4 × 4 km2 resolution data every 5–15 min, continuously. For ash detection, two channels situated near 11 and 12 μ m are needed; for ash quantification a third or fourth channel also in the infrared is useful for constraining the height of the ash cloud. This work describes passive EO infrared measurements and techniques to determine volcanic cloud properties and includes examples using current methods with an emphasis on the main difficulties and ways to overcome them. A challenging aspect of using satellite data is to design algorithms that make use of the spectral, temporal (especially for geostationary sensors) and spatial information. The hyperspectral sensor AIRS is used to identify specific molecules from their spectral signatures (e.g., for SO2) and retrievals are demonstrated as global, regional and hemispheric maps of AIRS column SO2. This kind of information is not available on all sensors, but by combining temporal, spatial and broadband multi-spectral information from polar and geo sensors (e.g., MODIS and SEVIRI) useful insights can be made. For example, repeat coverage of a particular area using geostationary data can reveal temporal behaviour of broadband channels indicative of eruptive activity. In many instances, identifying the nature of a pixel (clear, cloud, ash etc.) is the major challenge. Sophisticated cloud detection schemes have been developed that utilise statistical measures, physical models and temporal variation to classify pixels. The state of the art on cloud detection is good, but improvements are always needed. An IR-based multispectral cloud identification scheme is described and some examples shown. The scheme is physically based but has deficiencies that can be improved during the daytime by including information from the visible channels. Physical retrieval schemes applied to ash detected pixels suffer from a lack of knowledge of some basic microphysical and optical parameters needed to run the retrieval models. In particular, there is a lack of accurate spectral refractive index information for ash particles. The size distribution of fine ash (1–63 μ m, diameter) is poorly constrained and more measurements are needed, particularly for ash that is airborne. Height measurements are also lacking and a satellite-based stereoscopic height retrieval is used to illustrate the value of this information for aviation. The importance of water in volcanic clouds is discussed here and the separation of ice-rich and ash-rich portions of volcanic clouds is analysed for the first time. More work is required in trying to identify ice-coated ash particles, and it is suggested that a class of ice-rich volcanic cloud be recognized and termed a ‘volcanic ice’ cloud. Such clouds are frequently observed in tropical eruptions of great vertical extent (e.g., 8 km or higher) and are often not identified correctly by traditional IR methods (e.g., reverse absorption). Finally, the global, hemispheric and regional sampling of EO satellites is demonstrated for a few eruptions where the ash and SO 2 dispersed over large distances (1000s km).

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Atmospheric processes affecting the separation of volcanic ash and SO<sub>2</sub> in volcanic eruptions: inferences from the May 2011 Grímsvötn eruption

Cited by 50 publications

References 81 publications

Statistical analysis of dispersal and deposition patterns of volcanic emissions from Mt. Sakurajima, Japan

Statistical analysis of dispersal and deposition patterns of volcanic emissions from Mt. Sakurajima, Japan

The Evolution of Icelandic Volcano Emissions, as Observed From Space in the Era of NASA's Earth Observing System (EOS)

Passive Earth Observations of Volcanic Clouds in the Atmosphere

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