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| Titel |
Volcanic SO2 and SiF4 visualization using 2-D thermal emission spectroscopy – Part 2: Wind propagation and emission rates |
| VerfasserIn |
A. Krueger, W. Stremme, R. Harig, M. Grutter |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 6, no. 1 ; Nr. 6, no. 1 (2013-01-09), S.47-61 |
| Datensatznummer |
250017370
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| Publikation (Nr.) |
 copernicus.org/amt-6-47-2013.pdf |
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| Zusammenfassung |
| A technique for measuring two-dimensional (2-D) plumes of volcanic gases with thermal
emission spectroscopy was described in Part 1 by Stremme et al. (2012a). In that paper the instrumental aspects
as well as retrieval strategies for obtaining the slant column images of SO2 and SiF4, as
well as animations of particular events observed at the Popocatépetl volcano, were
presented. This work focuses on the procedures for determining the propagation speed of the gases
and estimating an emission rate from the given image sequences. A 2-D column density distribution
of a volcanic gas, available as time-consecutive frames, provides information of a projected wind field and
the average velocity at which the volcanic plume is propagating. This information is
valuable since the largest uncertainties when calculating emission rates of the gases using
remote sensing techniques arise from propagation velocities which are often inadequately assumed. The presented reconstruction
method solves the equation of continuity as an ill-posed problem using mainly a Tikhonov-like
regularisation. It is observed from the available data sets that if the main direction of
propagation is perpendicular to the line-of-sight, the algorithm works well for SO2, which has
the strongest signals, and also for SiF4 in some favourable cases. Due to the similarity of the
algorithm used here with the reconstruction methods used for profile retrievals based on optimal
estimation theory, diagnostic tools like the averaging kernels can be calculated in an analogous manner and
the information can be quantified as degrees of freedom. Thus, it is shown that the combination of
wind field and column distribution of the gas plume can provide the emission rate of the volcano
both during day and night. |
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