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PhD Defense

Jean-Baptiste MADELEINE (LMD)

Title : Dust and clouds on Mars: Remote sensing, modeling of climate feedbacks and paleoclimate applications

Date and time : The 04-02-2011 at 16h00

Type : thèse

Université qui délivre le diplôme :

Location : Amphithéâtre Herpin, Bâtiment Esclangon, campus de Jussieu
Members of jury :

Pascal RANNOU (GSMA/LATMOS), rapporteur

Peter READ (University of Oxford, UK), rapporteur

Hélène CHEPFER (LMD), Examinatrice

Thierry FOUCHET (LESIA), Examinateur

Nicolas MANGOLD (LPGNantes), Examinateur

Michael WOLFF (Space Science Institute, USA), Examinateur

François FORGET (LMD), Directeur de thèse

Summary :

The radiative impact of atmospheric dust and water ice clouds is the main driver of the martian climate. The ability to compute, during a simulation, the 3D evolution of the aerosol radiative properties as a function of the predicted size and spatial distribution of the particles is added to the LMD Mars Global Climate Model (GCM).

The model is first applied to atmospheric dust, and coupled to a dust transport scheme, which is guided by the observed dust opacity. New dust radiative properties are used, and connected to the predicted size of the dust particles. For the first time, the GCM temperatures are in good agreement with the observations, without any artificial tuning of the dust opacity, as was the case before.

The water cycle is then coupled to the dust cycle, and the radiative effect of water ice clouds is implemented. To better constrain the cloud properties, their diurnal evolution is mapped using the OMEGA imaging spectrometer, and the crystal size and opacity of the thickest clouds are retrieved. The GCM is then adjusted to these observations, and the radiative impact of clouds is assessed. Active clouds tend to dry out the whole water cycle, while at the same time removing the last significant temperature biases.

Finally we study the role of aerosols under past conditions, and a scenario for the origin of the northern mid-latitude glaciation is presented. The longitudinal distribution of the glacial deposits is explained, and the sensitivity of the glaciation to the orbital parameters, dust opacity, and ice thermal inertia is analyzed.

Contact :
LMD, Tour 45-55 3ème étage, campus de Jussieu; Tél. : 01 44 27 84 56, courriel : jbmlmd @ lmd.jussieu.fr
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