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| Titel |
Water ice cloud property retrievals at Mars with OMEGA:Spatial distribution and column mass |
| VerfasserIn |
Kevin S. Olsen, Jean-Baptiste Madeleine, Andre Szantai, Joachim Audouard, Anna Geminale, Francesca Altieri, Giancarlo Bellucci, Luca Montabone, Michael J. Wolff, François Forget |
| 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 |
250152325
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| Publikation (Nr.) |
 EGU/EGU2017-17148.pdf |
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| Zusammenfassung |
| Spectral images of Mars recorded by OMEGA (Observatoire pour la
Min\'{e}ralogie, l'Eau, les Glaces et l'Activit\'{e}) on Mars Express can be
used to deduce the mean effective radius ($r_\mathrm{eff})$ and optical depth
($\tau_\mathrm{i}$) of water ice particles in clouds. Using new data sets for \emph{a priori} surface temperature, vertical profiles of atmospheric temperature, dust opacity, and multi-spectral surface albedo, we have analyzed over 40 OMEGA image cubes over the Tharsis, Arabia, and Syrtis Major quadrangles, and mapped the spatial distribution of $r_\mathrm{eff}$, $\tau_\mathrm{i}$, and water ice column mass. We also explored the parameter space of $r_\mathrm{eff}$ and $\tau_\mathrm{i}$, which are inversely proportional, and the ice cloud index (ICI), which is the ratio of the reflectance at 3.4 and 3.52~$\mu$m, and indicates the thickness of water ice clouds. We found that the ICI, trivial to calculate for OMEGA image cubes, can be a proxy for column mass, which is very expensive to compute, requiring accurate retrievals of surface albedo, $r_\mathrm{eff}$, and $\tau_\mathrm{i}$. Observing the spatial distribution, we find that within each cloud system, $r_\mathrm{eff}$ varies about a mean of 2.1~$\mu$m, that $\tau_\mathrm{i}$ is closely related to $r_\mathrm{eff}$, and that the values allowed for $\tau_\mathrm{i}$, given $r_\mathrm{eff}$, are related to the ICI.
We also observe areas where our retrieval detects very thin clouds made of
very large particles (mean of 12.5~$\mu$m), which are still under
investigation. |
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