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| Titel |
Temporal variations of flux and altitude of sulfur dioxide emissions during volcanic eruptions: implications for long-range dispersal of volcanic clouds |
| VerfasserIn |
M. Boichu, L. Clarisse, J.-C. Péré, H. Herbin, P. Goloub, F. Thieuleux, F. Ducos, C. Clerbaux, D. Tanré |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 14 ; Nr. 15, no. 14 (2015-07-28), S.8381-8400 |
| Datensatznummer |
250119932
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| Publikation (Nr.) |
 copernicus.org/acp-15-8381-2015.pdf |
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| Zusammenfassung |
Sulfur-rich degassing, which is mostly composed of sulfur dioxide
(SO2), plays a major role in the overall impact of volcanism on the
atmosphere and climate. The accurate assessment of this impact is
currently hampered by the poor knowledge of volcanic SO2
emissions. Here, using an inversion procedure, we show how
assimilating snapshots of the volcanic SO2 load derived from the
Infrared Atmospheric Sounding Interferometer (IASI) allows for
reconstructing both the flux and altitude of the SO2 emissions with
an hourly resolution. For this purpose, the regional
chemistry-transport model CHIMERE is used to describe the dispersion
of SO2 when released in the atmosphere. As proof of concept, we
study the 10 April 2011 eruption of the Etna volcano (Italy), which
represents one of the few volcanoes instrumented on the ground for the
continuous monitoring of SO2 degassing.
We find that the SO2 flux time-series retrieved from satellite
imagery using the inverse scheme is in agreement with ground
observations during ash-poor phases of the eruption. However, large
discrepancies are observed during the ash-rich paroxysmal phase as
a result of enhanced plume opacity affecting ground-based ultraviolet
(UV) spectroscopic retrievals. As a consequence, the SO2 emission
rate derived from the ground is underestimated by almost one order of
magnitude.
Altitudes of the SO2 emissions predicted by the inverse scheme are
validated against an RGB image of the Moderate Resolution Imaging Spectroradiometer (MODIS) capturing the near-source
atmospheric pathways followed by Etna plumes, in combination with
forward trajectories from the Hybrid Single Particle Lagrangian
Integrated Trajectory (HYSPLIT) model. At a large distance from the
source, modelled SO2 altitudes are compared with independent
information on the volcanic cloud height. We find that the altitude
predicted by the inverse scheme is in agreement with snapshots of the
SO2 height retrieved from recent algorithms exploiting the high
spectral resolution of IASI. The validity of the modelled SO2
altitude is further confirmed by the detection of a layer of particles
at the same altitude by the spaceborne Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Analysis of
CALIOP colour and depolarization ratios suggests that these particles
consist of sulfate aerosols formed from precursory volcanic SO2.
The reconstruction of emission altitude, through inversion procedures
which assimilate volcanic SO2 column amounts, requires
specific meteorological conditions, especially sufficient wind shear
so that gas parcels emitted at different altitudes follow distinct
trajectories. We consequently explore the possibility and limits of
assimilating in inverse schemes infrared (IR) imagery of the volcanic
SO2 cloud altitude which will render the inversion procedure
independent of the wind shear prerequisite. |
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