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Portail > Offres > Offre FR636-EVEMAG-103 - Post-doctorant (H/F) en science du climat: Paramétrisation de l'impact des l'hétérogénéités de surface sous-maille sur le couplage mécanique entre la surface continentale et l'atmosphère dans les modèles de climat

Post-doctoral position (H/F) in science modelling: parameterizing the effect of subgrid-scale surface heterogeneity on the mechanical coupling between the atmosphere and the land surface in climate models.

This offer is available in the following languages:
Français - Anglais

Date Limite Candidature : lundi 10 avril 2023

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General information

Reference : FR636-EVEMAG-103
Nombre de Postes : 1
Workplace : PARIS 05
Date of publication : Tuesday, January 10, 2023
Type of Contract : FTC Scientist
Contract Period : 19 months
Expected date of employment : 1 April 2023
Proportion of work : Full time
Remuneration : From 2889,51 € to 4082,90 € gross according to expérience
Desired level of education : PhD
Experience required : 1 to 4 years


The objective of this work is to develop a parameterization of the surface drag exerted on the large-scale flow in the presence of sub-grid surface heterogeneity.


The recruited person will first analyze Large Eddy Simulations of typical atmospheric flows - i.e. simulations in which most of the small-scale turbulent motions, those which transport heat, moisture and momentum, are explicitly resolved - which have been run over heterogeneous terrains. Such simulations will make it possible to characterize the effective flow drag and the blending height according to various features of the terrain heterogeneity at different scales.
A first visit at CNRM will allow the student to become familiar with the LES and to begin to develop relevant diagnostics in the existing LES simulations.

Based on these results and on a thorough literature review on the wind drag over inhomogeneous surfaces a parameterization of the surface drag for the LMDZ general circulation model (atmospheric component of the IPSL-CM coupled climate model) will be developed.
Several options will be considered for the parameterisation but a simple and direct approach will be to find a new formulation of a so-called 'effective' roughness length. To develop, test and tune the new parameterization, Direct comparisons between LES and LMDZ simulations through the use of the SCM configurations will be possible on reference study cases as the one built on Darbieu (2015) in the framework of the MOSAI project (see below). However, a robust comparison between LMDZ in SCM mode and the LES requires the use of a common land-surface model. The implementation of a simplified surface model that can be connected to both LMDZ and LES will therefore be needed to take into account the coupling between the atmosphere and heterogeneous surfaces independently of the complexity of commonly-used LSM in climate models.
During a second visit at CNRM, the fellow will branch the simplified surface model in SURFEX (the surface modelling platform developed by Météo-France) in order to will produce MesoNH simulations coupled with a simplified surface module


- Ph.D. in climate science or atmospheric physics or surface-atmosphere exchange modeling or in atmospheric boundary layer processes
- Proven programming skills on UNIX machines.
- A good knowledge of Fortran and Python languages is strongly recommended.
- Able to work in collaboration with the members of the host team and the project.
- Application should be send with a CV, detailed letter of motivation describing the interest for the proposed research project and a complete list of scientific publications.

Work Context

EMC3 group (in Paris) with short stays ( 6 months out of 19 or 24 ) at CNRM/GMME/MOANA (Toulouse)
The EMC3 group (Study and Modeling of Climate and Climate Change) is one of the research groups of Laboratoire de Météorologie Dynamique (LMD). The activities of the EMC3 team are motivated by the desire to improve our understanding of the physical processes that govern the mean state and variability of the climate and to anticipate its future evolution. To this end, the team relies on a variety of observations and models, with various resolutions and complexity. In this context, an essential activity of the EMC3 group is the development of the LMDZ General Circulation Model (Hourdin et al., 2020}, the atmospheric component of the IPSL Earth System Model {Boucher et al., 2020}. A particular emphasis is placed on the development of `physical parameterisations': mathematically and physically consistent formulations of processes that are too fine-scale to be explicitly represented at model resolution. This concerns in particular cloud processes (Madeleine et al. 2020) and exchanges with continental surfaces {Cheruy et al. ,2020}. The EMC3 group maintains a close and long-lasting collaboration with the CNRM within the framework of the GDR DEPHY and several ANR (High Tune, MOSAI ... )

The present post-doctoral fellowship is funded by the 4-year MOSAI ANR project, which started in April 2021. The project aims to obtain an accurate assessment of the land-atmosphere exchanges at all scales, crucial step to better understand the global climate engine and its modelling. Three main scientific questions motivate the MOSAI project: (i) How to properly evaluate simulations of the land-atmosphere exchanges with local observations? (ii) Can we propose new methodologies for the observation-model comparison? (3) How to improve the land-atmosphere coupling representation in numerical weather prediction and climate models? The combination of new observations collected at three permanent instrumented sites and a wide suite of models from large-eddy simulations to climate models are used to address these questions.
- Duration of the contract from 19 to 24 months depending on experience.

Constraints and risks

6 months at the CNRM (Toulouse).

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