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| Titel |
Improving the accuracy of the SO2 camera |
| VerfasserIn |
Peter Lübcke, Christoph Kern, Leif Vogel, Felix Kick, Markus Wöhrbach, Ulrich Platt |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250042193
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| Zusammenfassung |
| The SO2 Camera is a novel technique to measure column densities and fluxes of SO2 emitted
by volcanoes using solar radiation scattered in the atmosphere as a light source. The
instrument is based on two interference band-pass filters and a UV-sensitive CCD
sensor.
A filter centered around 315 nm is used to measure the optical density of SO2in the
plume, whereas a second filter, centered around 330 nm, corrects the effects of aerosol
scattering and therefore makes the technique applicable to volcanic plumes containing
aerosols. The ability to deliver spatially resolved images of volcanic SO2 distributions at a
frame rate of the order of 1 Hz makes the SO2 camera a very promising technique for
monitoring the evolution of volcanic plumes, the quantitative determination of SO2 emissions
and flux measurements.
This poster explains the measurement principle and how to evaluate data measured with
the SO2camera. Several issues that can influence the measurement are addressed. For one, the
change in light path through the stratosphere with changing solar zenith angle changes the
spectral distribution measured on the earth’s surface. As the absorption of SO2 is highly
dependent on the wavelength of light, these changes can influence the measured column
densities. Secondly, as the camera uses scattered solar radiation as a light source, we
have to take radiative transfer effects in account. The path between the sun and the
instrument is not fixed, as effects like multiple scattering or ‘radiative dilution’ can
occur and lead to an underestimation or overestimation of the SO2 column density.
Recommendations for correcting the individual effects during data analysis are
given.
Aside from the above-mentioned intrinsic effects, there are several choices in the
technical setup of the SO2 camera which are discussed. A general description of the
instrument’s set-up and the camera control software are given. Finally, several measurement
examples are shown and possibilities to combine SO2 camera measurements with other
remote sensing techniques are explored. For example, a co-located DOAS system was used to
accurately calibrate the SO2-camera data in real time and to correct for the radiative transfer
effects. |
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