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| Titel |
Retrieval algorithm for densities of mesospheric and lower thermospheric metal atom and ion species from satellite-borne limb emission signals |
| VerfasserIn |
M. Langowski, M. Sinnhuber, A. C. Aikin, C. von Savigny, J. P. Burrows |
| 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 ; 7, no. 1 ; Nr. 7, no. 1 (2014-01-07), S.29-48 |
| Datensatznummer |
250115555
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| Publikation (Nr.) |
 copernicus.org/amt-7-29-2014.pdf |
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| Zusammenfassung |
| Meteoroids bombard Earth's atmosphere during its orbit around the Sun,
depositing a highly varying and significant amount of matter into the
thermosphere and mesosphere. The strength of the material source needs to be
characterized and its impact on atmospheric chemistry assessed. In this study
an algorithm for the retrieval of metal atom and ion number densities for a
two-dimensional (latitude, altitude) grid is described and explained. Dayglow
emission spectra of the mesosphere and lower thermosphere are used, which are
obtained by passive satellite remote sensing with the SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric
CHartographY) instrument on board
Envisat. The limb scans cover the tangent altitude range from 50 to 150 km.
Metal atoms and ions are strong emitters in this region and form sharply
peaked layers with a FWHM (full width at half maximum) of several 10 km in the mesosphere and lower
thermosphere measuring peak altitudes between 90 to 110 km. The emission signal
is first separated from the background signal, arising from Rayleigh and
Raman scattering of solar radiation by air molecules. A forward radiative
transfer model calculating the slant column density (SCD) from a given
vertical distribution was developed. This nonlinear model is inverted in an
iterative procedure to yield the vertical profiles for the emitting species.
Several constraints are applied to the solution for numerical stability
reasons and to get physically reasonable solutions. The algorithm is applied
to SCIAMACHY limb-emission observations for the retrieval of Mg and Mg+
using emission signatures at 285.2 and 279.6/280.4 nm, respectively. Results
are presented for these three lines as well as error estimations and
sensitivity tests on different constraint strength and different separation
approaches for the background signal. |
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