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| Titel |
Radiative transfer corrections for precise spectroscopic measurements of volcanic emissions |
| VerfasserIn |
C. Kern, T. Deutschmann, L. Vogel, M. Wöhrbach, T. Wagner, U. Platt |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250026273
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| Zusammenfassung |
| Passive remote sensing techniques are increasingly being applied to quantitatively measure
volcanic emissions. Well established techniques such as COSPEC, mobile DOAS, scanning
DOAS, imaging DOAS, and the SO2-camera all use sunlight scattered in the atmosphere as
a light source. Therefore, they measure the integrated column density of plume
components along the average optical path from the sun to the instrument. To obtain
gas concentrations or emission fluxes, however, the average optical path through
the volcanic plume must be known. Radiation scattered towards the instrument
without having passed through the plume can cause measurement errors. Also,
aerosols in volcanic plumes can cause an extension of the optical path, thereby
causing an overestimation of emissions. Recent model studies have shown that
radiative transfer in and around volcanic plumes can be highly variable and that
optical paths depend strongly on distance between plume and instrument, plume SO2
concentration, plume aerosol load, as well as aerosol conditions in the ambient
atmosphere.
Inaccurate knowledge of radiative transfer can result in significant measurement errors.
However, a method for retrieving optical path lengths in volcanic plumes was recently
developed and now allows the correction of these errors. The magnitude of radiative transfer
induced errors will be demonstrated using exemplary field measurements conducted with
both DOAS and SO2-camera techniques. By combining different measurement techniques
and applying the novel radiative transfer retrievals, volcanic emissions of SO2 (and other
trace gases) can be measured in real time, at a high temporal and spatial resolution, and at
high precision. |
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