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Reference : UMR3589-PASHAG-001
Workplace : ST MARTIN D HERES
Date of publication : Thursday, September 05, 2019
Type of Contract : FTC Scientist
Contract Period : 12 months
Expected date of employment : 1 November 2019
Proportion of work : Full time
Remuneration : Between 2617 et 3017 euros gross monthly salary
Desired level of education : PhD
Experience required : Indifferent
Snow is at the interface between the atmosphere and the continental and oceanic surfaces of high latitudes and significantly affects their energy and water balance. In particular, the snow thermally isolates the surfaces it covers. This insulating power is quantified by the snow thermal conductivity, a property which is difficult to measure reliably and continuously in remote areas such as the Arctic. Besides, the temperature gradient typically observed in arctic and sub- arctic snowpacks leads to a vertical flow of water vapor that transfers this compound from the soil and snowpack to the atmosphere. This essential process in the hydrological balance of the cold regions is for the moment imprecisely quantified. Recent developments in microstructural imaging and analysis of snow provide a detailed understanding of the phenomena of heat and matter transport in snow. This opens up important possibilities to evaluate measurement and modeling techniques related to these processes and finally to more precisely parameterize the physical models of snow and climate. This PhD project aims to improve the understanding and quantification of : (1) heat transport processes when measuring the thermal conductivity of snow by heated needle. This method, which is the only one applicable today in automatic mode, is suspected to present artifacts which needs to be quantified and corrected by developing a suitable algorithm. (2) diffusion of water vapor in snow. This phenomenon involves sublimation-condensation processes of ice crystals which significantly contribute to the transfer but has not been quantified so far. Quantifying an apparent diffusion coefficient of water vapor is critical to simulate snow metamorphism, and thus all its physical properties, as well as the hydrological balance of snow-covered surfaces.
The project involves experimental work in cold laboratory using X-ray tomography imaging of snow samples combined
with measurements of thermal conductivity and mass transfer; and multi-physics numerical modeling with finite
elements using 3D images of snow microstructure as input.
This opportunity is suited for a candidate with a quantitative background in (geo)physics, material sciences, applied mathematics, geoscience, or a related discipline. This project requires skills in numerical modeling (finite element, especially) and image processing. Field and cold-lab measurements are also part of the project and require specific motivations for cold and snow.
The CNRM is the research center of Météo-France, it is a mixed unit of the CNRS. With about 230 permanent staff, its mission is to develop the knowledge and tools that Météo-France needs to produce its forecasts of weather, air quality or climate. One of the six units forming the CNRM, the CEN focuses on the study of snow. With about twenty permanent staff, CEN has been involved for many years in the study of the microstructure of snow and processes taking place at this scale. The work will be supervised by Pascal Hagenmuller (CNRM / CEN) and Florent Domine (Takuvik Joint International Laboratory).
Constraints and risks
Experiment in cold room (-15°C°).
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