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Reference : UMR5306-ALAMIF-005
Workplace : VILLEURBANNE
Date of publication : Wednesday, January 13, 2021
Type of Contract : FTC Scientist
Contract Period : 12 months
Expected date of employment : 8 February 2021
Proportion of work : Full time
Remuneration : From 1600 to 2000 euros
Desired level of education : 5-year university degree
Experience required : Indifferent
Scientific context and motivations
As underscored by the latest IPCC report (IPCC, 2013), atmospheric aerosols are complex physical objects that may somewhat counterbalance the warming effect of most greenhouse gases. However, to draw such a conclusion, the interaction of light with such complex systems should be first quantified. The dust aerosol is indeed a complex physical object, presenting a wide range of sizes, a highly irregular shape, sometimes with sharp edges and surface roughness, which prevents from analytical solutions to the Maxwell's equations (Mishchenko et al., 2002), thus limiting our ability to quantify the interaction of such complex systems with the electromagnetic field. Light scattering numerical simulations exist but rely on assumptions that should be carefully checked. Hence, while light backscattering is of prime importance as involved in future satellite lidar missions (MESCAL, Earth Care or ACCP) as underscored by CNES in France, it is only recently that light backscattering has been observed in laboratory for particles embedded in ambient air (Miffre et al., 2016) where a unique (UV, VIS) polarimeter operating at specific lidar Pi-backscattering angle has been designed. This Pi-polarimeter quantifies the particles deviation from isotropy through accurate particle depolarization ratio (PDR)-measurements. Not only polarimetry is involved but also spectroscopy as PDR-measurements are currently performed at several wavelengths, covering the UV and VIS spectral ranges (Miffre et al., 2016).
The present call is aimed at extending this unique laboratory Pi-polarimeter to the IR spectral range to quantify the PDR-spectral dependence, which is key for aerosol identification (Burton et al., 2016). More precisely, fundamental laboratory intensive work is required to address the dust aerosol PDR at exact backscattering angle for each definite property (size, origin). Such unique laboratory measurements of the intrinsic dust PDR will then be made available to a broad scientific community, in France and abroad through publications and conferences.
Burton, S. et al., Atmos. Chem. Phys., 15, 13453-13473, (2016).
IPCC, Intergovernmental Panel for Climate Change: the Physical Science Basis. (2013).
Mishchenko, M. I. et al.: Scattering, Absorption, and Emission of Light by Small Particles, Cambridge, (2002).
Miffre, A., T. Mehri, M. Francis and P. Rairoux, UV-VIS depolarization from Arizona Test Dust particles at exact backscattering angle, J. Quant. Spec. Rad. Transf., 169, 45-59, (2016).
Starting from the existing laboratory Pi-polarimeter (Miffre et al., 2016), the candidate will then
- Contribute to develop a Pi-polarimeter in the IR spectral range.
- Minimize polarization and wavelengths cross-talks in the hence built multi-spectral polarimeter.
- Evaluate the variation in the dust aerosol PDR (particle depolarization ratio, see above missions for details) as a function of the dust particle size and mineralogy to reveal the intrinsic PDR of mineral dust by accounting for its complexity.
To carry out this research project, candidates must hold a PhD in optics (polarimetry, spectroscopy, laser physics) and/or atmospheric physics (atmospheric aerosols, satellite remote sensing). Above all, precision is required to reveal the intrinsic ability of this complex aerosol to depolarize laser light.
The ILM is a joint research unit between the University of Lyon (UCBL) and the Centre National de la Recherche Scientifique (CNRS) which includes about 285 people divided between researchers, teacher-researchers, research support staff, doctoral and post-doctoral students. The ILM is composed of 17 research teams organized along six thematic axes, addressing topics ranging from solid state physics and nanosciences to ultrafast optics and matter-light interaction. The ILM is located on the Lyon Tech La Doua Campus in Villeurbanne.
The research activity will be achieved under the supervision of A. Miffre from the ATMOS research group (Prof. Rairoux group leader). This 12 months' position funded by CNES will be located at the Institute of Light and Matter (iLM) under the supervision of A. Miffre from the ATMOS research group (Prof. Rairoux group leader).
Constraints and risks
Laser and aerosols safety.
For further information, please contact :
Associate Professor in Physics at iLM
Atmos Research group at ILM (Prof. Rairoux's group)
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