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| Titel |
Imaging trace gases in volcanic plumes with Fabry Perot Interferometers |
| VerfasserIn |
Jonas Kuhn, Ulrich Platt, Nicole Bobrowski, Peter Lübcke, Thomas Wagner |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250143174
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| Publikation (Nr.) |
 EGU/EGU2017-6875.pdf |
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| Zusammenfassung |
| Within the last decades, progress in remote sensing of atmospheric trace gases revealed many
important insights into physical and chemical processes in volcanic plumes. In
particular, their evolution could be studied in more detail than by traditional in-situ
techniques.
A major limitation of standard techniques for volcanic trace gas remote sensing (e.g.
Differential Optical Absorption Spectroscopy, DOAS) is the constraint of the measurement to
a single viewing direction since they use dispersive spectroscopy with a high spectral
resolution. Imaging DOAS-type approaches can overcome this limitation, but become very
time consuming (of the order of minutes to record a single image) and often cannot match the
timescales of the processes of interest for volcanic gas measurements (occurring at the order
of seconds).
Spatially resolved imaging observations with high time resolution for volcanic sulfur dioxide
(SO2) emissions became possible with the introduction of the SO2-Camera. Reducing the
spectral resolution to two spectral channels (using interference filters) that are matched to the
SO2 absorption spectrum, the SO2-Camera is able to record full frame SO2 slant column
density distributions at a temporal resolution on the order of < 1s. This for instance allows for
studying variations in SO2 fluxes on very short time scales and applying them in magma
dynamics models. However, the currently employed SO2-Camera technique is limited
to SO2 detection and, due to its coarse spectral resolution, has a limited spectral
selectivity. This limits its application to very specific, infrequently found measurement
conditions.
Here we present a new approach, based on matching the transmission profile of Fabry Perot
Interferometers (FPIs) to periodic spectral absorption features of trace gases. The FPI’s
transmission spectrum is chosen to achieve a high correlation with the spectral absorption of
the trace gas, allowing a high selectivity and sensitivity with still using only a few spectral
channels. This would not only improve SO2 imaging, but also allow for the application of the
technique to further gases of interest in volcanology (and other areas of atmospheric
research).
Imaging halogen species would be particularly interesting for volcanic trace gas studies.
Bromine monoxide (BrO) and chlorine dioxide (OClO) both yield absorption features that
allow their detection with the FPI correlation technique. From BrO and OClO data, ClO
levels in the plume could be calculated.
We present an outline of applications of the FPI technique to imaging a series of trace gases
in volcanic plumes. Sample calculations on the sensitivity and selectivity of the
technique, first proof of concept studies and proposals for technical implementations are
presented. |
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