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| Titel |
Accounting for the effect of horizontal gradients in limb measurements of scattered sunlight |
| VerfasserIn |
J. Puķīte, S. Kühl, T. Deutschmann, U. Platt, T. Wagner |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 8, no. 12 ; Nr. 8, no. 12 (2008-06-20), S.3045-3060 |
| Datensatznummer |
250006216
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| Publikation (Nr.) |
 copernicus.org/acp-8-3045-2008.pdf |
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| Zusammenfassung |
Limb measurements provided by the SCanning Imaging Absorption spectrometer
for Atmospheric CHartographY (SCIAMACHY) on the ENVISAT satellite allow
retrieving stratospheric profiles of various trace gases on a global scale,
among them BrO for the first time. For limb observations in the UV/VIS
spectral region the instrument measures scattered light with a complex
distribution of light paths: the light is measured at different tangent heights
and can be scattered or absorbed in the atmosphere or reflected by the
ground. By means of spectroscopy and radiative transfer modelling these
measurements can be inverted to retrieve the vertical distribution of
stratospheric trace gases.
The fully spherical 3-D Monte Carlo radiative transfer model "Tracy-II" is applied
in this study. The Monte Carlo method benefits from conceptual simplicity and
allows realizing the concept of full spherical geometry of the atmosphere and
also its 3-D properties, which is important for a realistic description of the
limb geometry. Furthermore it allows accounting for horizontal gradients in
the distribution of trace gases.
In this study the effect of horizontally inhomogeneous distributions of trace
gases along flight/viewing direction on the retrieval of profiles
is investigated. We introduce a tomographic method to correct for this effect by
combining consecutive limb scanning sequences and utilizing the overlap in
their measurement sensitivity regions. It is found that if horizontal
inhomogenity is not properly accounted for, typical errors of 20% for
NO2 and up to 50% for OClO around the altitude of the profile peak can
arise for measurements close to the Arctic polar vortex boundary in boreal
winter. |
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