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PhD student in planetology (male/female)

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Français - Anglais

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General information

Reference : UMR8190-ANNMAA-001
Workplace : PARIS 05
Date of publication : Monday, January 28, 2019
Scientific Responsible name : Anni MÄÄTTÄNEN
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2019
Proportion of work : Full time
Remuneration : 1 768,55 € gross monthly

Description of the thesis topic

Detailed thesis subject:

Clouds are one of the most complex meteorological objects to model in a planetary atmosphere, due to the wide range of spatial and temporal scales at play, from the molecular nucleation stage to the large cloud cover spanning thousands of kilometers, and cloud modelling has been identified as the main challenge in Earth climate simulations by IPCC [1].
CO2, the main constituent of the Martian atmosphere, is known to condense on the polar caps and as clouds in the atmosphere (polar troposphere and equatorial mesosphere). These clouds have been observed for more than a decade, but their modeling is a real challenge. In the mesosphere, the scarcity of condensation nuclei and the low density of the atmosphere require a re-evaluation of the theories of microphysics. In the polar troposphere, the clouds are of convective type and/or generated by waves and the coupling between the dynamics and the released latent heat is especially fast and intense.

State-of-the-art :
Several years of work at LATMOS on the modeling of the CO2 cloud microphysics in the Martian atmosphere have led to the development of an unprecedented tool: a model of CO2 cloud microphysics for the Martian atmosphere [2,3]. The full microphysical scheme has recently been incorporated into the Mars Global Climate Model (MGCM) of the LMD, developed in collaboration between LATMOS and LMD. The first global simulations of CO2 cloud formation in the Martian mesosphere have thus been obtained and compared to the observed climatology (Mars Express, Mars Reconnaissance Orbiter…). Today the LMD-MGCM is the most advanced model for studying the Martian CO2 ice clouds thanks to its fine microphysics, the high model top (150 km) that enables the realistic modeling of the middle and upper atmosphere, and a correct treatment of condensation and its consequences in the polar regions. In addition the LMD-MGCM and the Martian mesoscale model (MMM) that has also been developed at the LMD share the same physical parameterizations, allowing for immediate transfer of the new microphysical scheme to the MMM. The MMM model that is used in higher resolution than the MGCM but in a more limited zone allows for using even higher spatial and temporal resolutions (Cloud Resolving Model, CRM, ou Large-Eddy Simulation, LES), necessary for studying convective processes.

The project aims at responding to the following scientific question :
What are the dynamical processes and feedbacks at play in the formation and evolution of the polar CO2 ice clouds, and the triggering of snowfall?

The project is based on the spectrum of modeling tools we have at hand within the team: here more precisely the limited-area high-resolution mesoscale model MMM and its very high-resolution CRM version.

The PhD thesis will focus on the tropospheric winter clouds in the polar regions. These clouds are convective and/or generated by atmospheric waves, and the coupling between the dynamics and the latent heat release is strong. Because of the small scale of these phenomena and the dynamics involved the use of a mesoscale or a cloud-resolving model becomes necessary. Our team has performed ground-breaking studies on similar phenomena with these tools [4,5]. The latent heat release has a strong impact on the cloud dynamics through the moist convection process. The convective processes will be studied with the high-resolution CRM model and the wave influence on the cloud formation with the lower resolution mesoscale and/or the global model. The study can allow us also to explain on a fundamental level the effect of latent heat release on the polar vortex dynamics [6]. This kind of study on moist convection-mean flow interaction in the polar regions has never been attempted before and would produce outstanding results.

The PhD student will need to learn to use the MMM and CRM models (as well as possibly the MGCM) and to validate the CO2 cloud microphysics in the mesoscale configuration in the polar regions. This will be done by performing the first mesoscale simulations with the CO2 microphysics and comparing the results to those of the MGCM (that exist already) and to published observations [7,8,9]. Once this first validation step has been done, the next will be to increase the model resolution, thus reaching the CRM resolution, and to perform the first simulations with this configuration.

After the validation phase of the MMM and the CRM with CO2 microphysics in a polar configuration (first 6 months), the project will continue in two phases (of approximately one year each). The first part will concentrate on the CRM and the study of the moist convection. The second part will try to clarify the influence of the latent heat released by condensation on the large-scale dynamics.

This work will also require visualizing the simulation results and their analysis, which will be done with the Python tools developed at the LMD.

We expect 2-3 articles to be published during the thesis and potentially 1-2 others after the thesis.

Profile and skills required:
Master (M2) in atmospheric physics, planetology, astrophysics or equivalent. Solid background in mathematics and physics (preferentially in atmospheric physics). Good skills in informatics and experience in programming and in atmospheric modeling (Fortran) are an asset. Capability to work both in a team and autonomously. Good level in English is highly recommended (necessary for reading literature, giving oral presentations in international conferences and writing abstracts and scientific articles).

Please note that although the applications are to be sent via the CNRS portal (deadline May 1st 2019), the inscription to the university needs to be done via the Doctoral school 127:

[1] Boucher, O., et al., 2013 : Clouds and Aerosols. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.
[2] Listowski, C. et al. 2013, J. Geophys. Res. 118, 2153-2171, doi:10.1002/jgre.20149.
[3] Listowski, C. et al. 2014, Icarus 237, 239-261, doi:10.1016/j.icarus.2014.04.022.
[4] Spiga A., et al. 2013, J. Geophys. Res. 118, 746-767, doi:10.1002/jgre.20046.
[5] Spiga, A., et al. 2017, Nature Geosci. 10, 652–657 doi: 10.1038/NGEO3008.
[6] Toigo, A.D. et al. 2017, Geophys. Res. Lett. 44, 71–78, doi : 10.1002/2016GL071857.
[7] Pettengill, G.H., Ford, P.G., 2000. Geophys. Res. Lett. 27, 609–612.
[8] Ivanov, A.B., Muhleman, D.O., 2001. Icarus 154, 190–206.
[9] Hayne, P.O. et al. 2014, Icarus 231, 122-130, doi :10.1016/j.icarus.2013.10.020.

Work Context

The LATMOS laboratory (UMR8190) is a joint research unit specializing in the study of fundamental physical and chemical processes governing the terrestrial and planetary atmospheres and their interfaces with the surface, the ocean, and the interplanetary medium. It is situated on two sites, in Paris (campus UPMC, Sorbonne université, Jussieu) and in Guyancourt (Yvelines), hosting >200 personnes.
The student will be hosted by the planetologty department and it planetary atmospheres team, composed of 4 permanent research scientists. The thesis will be co-supervised between the LATMOS (A. MAATTANEN, LATMOS) and the LMD laboratories (A. SPIGA, LMD).

Additional Information

The thesis is funded by the ANR (French research agency)

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