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Température et composition de la stratosphère de Saturne à partir des données de Cassini/CIRS

Abstract : The goal of this thesis is to measure the temperature and composition fields in Saturn's stratosphere. In order to do so, we analyze spectra of the thermal emission of the planet acquired in limb geometry by CIRS, an infrared spectrometer aboard the Cassini spacecraft. These spectral signatures are analyzed using a radiative transfer model coupled to a retrieval algorithm in order to measure vertical profiles of the temperature and of the abundance of atmospheric gases. We have thus obtained the first maps, from 70° N to 80° S, and on several scale heights, of the temperature and abundance of five hydrocarbons: ethane , acetylene, propane, methylacetylene and diacetylene. The temperature map we obtain is used to quantify the thermal response of the atmosphere to seasonal variations in insolation. We compare the gradients we measure to the radiative seasonal model of Greathouse et al., 2008. We also report the discovery of an equatorial oscillation in temperature and zonal wind profiles in the stratosphere of Saturn, similar to the Earth's quasi-biennial oscillation, and we present its temporal evolution between 2005 and 2010. The analysis of the hydrocarbons' distributions and their comparison to a seasonal photochemical model (Moses et al., 2005) show signs of meridional transport in the lower stratosphere and vertical transport in the upper stratosphere. We also determine the abundance of CO2 at 4 latitudes, which presents an enrichment at the equator. Finally, we present a detailed analysis of radiative exchanges in the stratosphere using the Net Exchange Rates formulation. This work will form the basis for a future parameterization of radiative transfer computation, a necessary step in developing a general circulation model of Saturn's stratosphere.
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https://tel.archives-ouvertes.fr/tel-00551919
Contributor : Sandrine Guerlet <>
Submitted on : Tuesday, January 4, 2011 - 9:57:28 PM
Last modification on : Friday, December 18, 2020 - 4:02:02 PM
Long-term archiving on: : Monday, November 5, 2012 - 3:30:13 PM

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  • HAL Id : tel-00551919, version 1

Citation

Sandrine Guerlet. Température et composition de la stratosphère de Saturne à partir des données de Cassini/CIRS. Planète et Univers [physics]. Observatoire de Paris, 2010. Français. ⟨tel-00551919⟩

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