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Reference : UMR8190-ANNMAA-002
Workplace : PARIS 05
Date of publication : Tuesday, January 29, 2019
Type of Contract : FTC Scientist
Contract Period : 24 months
Expected date of employment : 1 September 2019
Proportion of work : Full time
Remuneration : 2100-2400 €/month net
Desired level of education : PhD
Experience required : 1 to 4 years
We are proposing a two-year full-time postdoctoral fellowship on modeling the Martian mesospheric CO2 clouds with a global climate model.
Mars is the second most observed planet in our Solar System, and we are gradually starting to
understand the intricacies of its atmosphere at a detailed level. Thanks to the flood of data,
several mysteries are being uncovered. One of the latest sources of intrigue is the condensation
of the main constituent of the atmosphere (CO2) as clouds. The formation of these clouds
forces us to revise microphysical theories to account for the fact that the condensing species is
not a trace gas but a nearly pure vapor, and to reflect upon the possible dynamical phenomena
caused by the formation of these clouds. Cloud observations have been collected during more
than a decade, and today there are several complementary climatologies on mesospheric (CO2) clouds that set the basis for understanding their formation and evolution, and their role in the Martian climate. As the fruit of ten years of effort our team has built a unique microphysical
model for CO2 that has now been coupled with the 3D atmospheric models for Mars of
the LMD laboratory. With this unique tool, we are now ready to answer fundamental questions on the formation of Martian CO2 clouds. Our project is funded by the French research agency ANR (ANR JCJC project “MECCOM”) for 3.5 years.
The necessary ingredients giving rise to the formation of mesospheric clouds have been studied
with GCMs with and without microphysics (Colaprete et al. 2008 ; Gonzalez-Galindo et al. 2011) and with idealized, theoretical studies (Spiga et al. 2012). Some studies (Colaprete et al. 2008 ; Yigit et al. 2015) failed in reproducing the observed distribution of mesospheric clouds, but
the studies done with the earlier versions of the modeling tools to be used in this MECCOM
project (Gonzalez-Galindo et al. 2011 ; Spiga et al. 2012) pioneered in confirming that the mesospheric clouds very probably form in supersaturated pockets created by the superposition of planetary scale thermal tides and gravity waves propagating to the mesosphere. However, in these studies planetary and mesoscale processes were not coupled, and no supersaturation was attained in the global model because the gravity wave effect on the temperatures was not accounted for.
Recently our group has developed a state-of-the-art microphysical column (1D) model for
CO2 clouds (Listowski et al. 2013 ; Listowski et al. 2014). The coupling of this model to the Mars Global Climate Model (MGCM) developed jointly by LATMOS and LMD laboratories (Forget et al. 1999 ; Navarro et al. 2014) was achieved by our team and our close collaborators in 2017 (Audouard et al. 2017). Today, the MGCM is the most advanced tool available for studying the CO2 ice clouds on Mars.
The post-doctoral project is twofold:
1) CO2 cloud ice nucleus sources and their properties in the mesosphere: (1)Investigate the relative roles of the different mesospheric ice nucleus sources on cloud formation; (2) quantify the amount of water vapor and water ice in the mesosphere from MGCM simulations and re-evaluate the formation of magnesium hydrates (potential ice nuclei); (4) update the nucleation parameters of mesospheric ice nuclei and re-appraise the cloud formation pathways.
2) Variability of mesospheric clouds: (1) quantify the occurrences of supersaturated pockets in the mesosphere from SPICAM stellar occultation data and detect simultaneous mesospheric clouds; (2) study the impact of interannual variations of dust optical thickness on the mesospheric cloud occurrences with the MGCM; (3) revise the current gravity wave and subgrid scale temperature variation parametrization in the MGCM
The project aims at modeling, for the first time, in a fully-consistent manner all aspects of CO2 ice cloud formation by including all sources of mesospheric ice nuclei and integrating the latest results from observations and numerical and laboratory experiments.
The post-doctoral fellow, supervised by Dr. A. Määttänen, will carry out new dynamical and microphysical simulations with the three-dimensional MGCM, developed in collaboration with the LATMOS and the LMD laboratories, including CO2 cloud microphysics adapted to Mars (built by LATMOS).
The main scientific question the project aims at answering is: What are the dynamical and microphysical factors governing the inter-annual variations and spatial distribution of the mesospheric clouds, including the sources of nuclei? This can be more precisely divided in two sub-questions: What are the relative contributions of meteoritic particle injections and dust lifted from the surface to the ice nucleus inventory of the mesosphere? How can we explain the numerous observed supersaturated temperature profiles lacking the presence of a cloud? The post-doctoral fellow will focus on providing answers to these questions during his/her stay in LATMOS.
We are looking for candidates with an expertise in planetary or terrestrial atmospheric sciences and modeling. Previous experience in cloud microphysics as well as in programming (Fortran, Python) is highly recommended. Experience in data analysis is an advantage. Good team-working skills together with an independent and curious mind are expected. Good level of spoken and written English is required, and knowing some French will be helpful although not required.
The post-doctoral fellow will join the ANR-funded team at the LATMOS laboratory in Paris, at the UPMC campus of the Sorbonne university in Jussieu, working on a project led by Dr. Anni Määttänen and nested in a regional and international network.
The post-doctoral fellow will be able to conduct his/her project in a strong scientific network between LATMOS and LMD laboratories (France), University of Leeds (UK) and Instituto de Astrofísica de Andalucía (Spain). In addition to the modeling work, the post-doctoral fellow will participate in an experimental laboratory measurement campaign at the University of Leeds on the CO2 nucleation properties of mesospheric ice nuclei, and study the mesospheric temperatures by using observations from the SPICAM instrument (Mars Express). The project will also provide the post-doctoral fellow funding for travelling to international meetings.
Financed by the ANR.
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