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Portail > Offres > Offre FR636-EVEMAG-069 - Chercheur.se pour études des processus physiques pilotant le cycle de vie des brouillards (H/F)

Researcher for studies of the physical processes controlling the life cycle of fog (M/F)

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

Date Limite Candidature : mardi 1 février 2022

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General information

Reference : FR636-EVEMAG-069
Workplace : GUYANCOURT
Date of publication : Tuesday, January 11, 2022
Type of Contract : FTC Scientist
Contract Period : 12 months
Expected date of employment : 1 March 2022
Proportion of work : Full time
Remuneration : From 2743, 70 € to 3896,74 € gross according to expérience
Desired level of education : PhD
Experience required : 1 to 4 years

Missions

Study precisely from observations and numerical simulations the role of several processes (radiative, thermodynamic, microphysical) on the evolution of the water content of the fog and its structure and its vertical extent during the dissipation phase of the fog.

Activities

The project proposed here has four main stages and activities:

1. Prepare observation datasets for 3 case studies, and use these observations to describe each case based on a conceptual model. Study the variability of key variables during the dissipation phase (intensity of inversion at the top of the fog, water content, geometric thickness, surface flux, turbulence measurements).

2. Validate more finely the “Large Eddy Simulations” (LES) from all the observations but focusing on the dissipation phase. Study in particular the evolution of the vertical redistribution of liquid water (including droplets and drizzle and monitoring of geometric thickness, using cloud radar and range finder) in the dissipation phase (critical for the lifting of fog).

3. Quantify and analyze the role of each physical process from the balance sheets of the model's prognostic variables such as cloud water and water vapor content, potential temperature and turbulent kinetic energy (including the contribution of turbulent flows to these reports).

4. Apply the conceptual model to the model variables. The changes in the water content simulated in LES will be compared with the change in the water content simulated according to the conceptual model "LWP-C", fed as input by the observations or by the simulated fields, in order to validate and improve if necessary the conceptual model.

Skills

- Doctorate in climate science or meteorology or equivalent
- Scientific research experience in an academic environment as part of a thesis and possibly a postdoc
- Knowledge of measurement systems or digital simulations of the atmosphere
- Good capacity for teamwork, autonomy and rigor in the work
- Good level of oral and written communication in French and English

Work Context

As part of the SOFOG-3D measurement campaign that took place in 2018, the Pierre Simon Laplace Institute (Paris) and the National Meteorological Research Center (Toulouse) wish to work together on a better understanding of processes and values reviews of certain variables that may or may not favor the dissipation of so-called adiabatic mists.
The dissipation of continental fogs is an important phase because it often takes place during the day, therefore over a period of the day when human activities are strongly impacted. We have shown via a conceptual model that in a so-called adiabatic fog: i) the altitude of the fog top (CTH), the water content of the integrated fog (LWP), the visibility at the surface, and the temperature and pressure are related, and ii) that imminent dissipation may be associated with the water content of the integrated fog compared to a critical value (Toledo et al. 2021). The conceptual model approach is valid for well-mixed adiabatic mists, as it assumes vertically homogeneous temperature changes. Since the conceptual model is one-dimensional, it will be important to study the impact of 3D processes such as horizontal transport on its validity.
We therefore wish to study more precisely the role of entrainment at the top of the fog, subsidence, radiative cooling, radiative absorption, droplet deposition and the energy balance at the base of the fog on the evolution of the balance. LWP, LWC profile and CTH in dissipation phase. We will rely for this on two data sources:
- detailed observations of the SOFOG-3D campaign, such as measurements of turbulence and microphysics under a captive balloon, on mast and on the surface, measurements of cloud radars and microwave radiometers. A thesis is also in progress on the validation and analysis of microphysics during the campaign.
- so-called LES (“Large Eddy Simulations”) simulations obtained with the Meso-NH model (Lac et al., 2018) on the best documented cases at spatial resolutions of around ten meters. A preliminary work of another post-doc will have made it possible to define the best configuration and to validate the LES simulations from the main observations of the campaign.

Employment situation and conditions:
Location: Palaiseau Polytechnic School and teleworking

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