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| Titel |
Radiative transfer effects of high SO2 and aerosol loads during major volcanic eruptions |
| VerfasserIn |
Christoph Hörmann, Marloes Penning de Vries, Steffen Beirle, Thomas Wagner |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250098610
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| Publikation (Nr.) |
 EGU/EGU2014-14302.pdf |
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| Zusammenfassung |
| Satellite remote sensing of volcanic emissions nowadays allow to globally track and quantify
large plumes after major eruptions. Especially the detection of sulphur dioxide (SO2) via
Differential Optical Absorption Spectroscopy (DOAS) has become one of the most
common applications to monitor the input of gaseous volcanic species into the Earth’s
atmosphere.
While SO2 can be spectroscopically identified because of its strong absorption bands in the
UV, the DOAS method can usually only be applied for optical weak absorbers. However, if
the SO2 loading of the atmosphere becomes very high, which may occur in the course of a
strong volcanic eruption, the atmosphere can no longer be considered transparent
throughout the commonly used wavelength range of evaluation between 300 and 325
nm. The associated radiative transfer usually results in a strong underestimation
of the SO2 slant column density (SCD), mainly because the solar radiation that
is detected by the satellite instruments has only penetrated the outermost layers
of the SO2-rich volcanic plume. In order to overcome this problem, we recently
proposed to use a combination of results from the standard and additional alternative fit
windows at longer wavelengths (326.5-335 nm and/or 360-390 nm). Here, the SO2
absorption cross-section is generally weak, but sufficiently strong for the detection
of very high SO2 loads. A first comparison of the results showed that generally a
typical relationship can be identified between SO2 SCDs from different evaluation
wavelength ranges. However, occuring differences for some observations can only be
explained by the additional influences of large amounts of volcanic aerosols on radiative
transfer.
We present first results from a study on the possible characterisation of volcanic aerosol
properties and thereby associated impacts of the radiative transfer on the SO2 DOAS retrieval
at different fit windows. Satellite observations of the SO2 column densities and UV Aerosol
Indices (UVAI) by the Ozone Monitoring Instrument (OMI) as well as the Global Ozone
Monitoring Instrument (GOME-2) will be analysed and supported by simulations with the
Monte-Carlo radiative transfer model McArtim for the volcanic eruption of the Kasatochi
volcano in August 2008. |
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