Polarization-resolved backscattering from nanoparticles in the atmosphere : field and laboratory experiments

• Main Author: David, Gregory
• Other Authors: Institut Lumière Matière Villeurbanne (ILM), Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS), Université Claude Bernard - Lyon I, Patrick Rairoux, Alain Miffre
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2013
• Subjects: Atmosphere; Dielectric nanoparticles; Backscattering of light; Multispectral lidar; Greenhouse gases; Nanoparticules diélectriques; Atmosphère; Rétrodiffusion de la lumière; Lidar multi-spectral; Gaz à effet de serre; [PHYS.PHYS.PHYS-AO-PH]Physics [physics]/Physics [physics]/Atmospheric and Oceanic Physics [physics.ao-ph]; Eyjafjallajökull
• Online Access: https://tel.archives-ouvertes.fr/tel-01146445; https://tel.archives-ouvertes.fr/tel-01146445/document; https://tel.archives-ouvertes.fr/tel-01146445/file/TH2013DavidGregory.pdf

Atmospheric greenhouse gases and nanometer-sized particles are incriminated for their role on the Earth radiative budget and climate. This thesis relates the research performed on thepolarization-resolved backscattering of these nano-sized particles and demonstrates itsusefulness to address complex atmospheric processes like particles nucleation. Greenhouse gases are also studied, by coupling a spectrally broadband lidar with optical correlation spectroscopy to remotely evaluate their atmospheric content (Thomas et al., 2012, 2013a,b). Special care has been taken to perform sensitive and accurate UV-VIS polarization lidar measurements (David et al., 2012). Hence, and as a first result, cross-polarized backscattering coefficients as low as (2.4 ± 0.5)×10−8 m−1.sr−1 have been measured in the troposphere, corresponding to UV-particles depolarization detection limit of 0.6 % at 4 km altitude, close to the molecular depolarization. Then, a new methodology has been developed to retrieve, in atwo/three component particle external mixture, the backscattering coefficients specific to eachparticle component (David et al., 2013a). For that purpose, accurate knowledge on the backscattering Ångstrom exponent and depolarization ratio of each particle type must beaddressed. This task is here achieved by performing either single-scattering numerical simulations using T-matrix, or alternatively by performing laboratory measurements. Thei nherent assumptions and the performance of the methodology are then discussed for three case studies of external mixing: i) spherical sulfate mixed with volcanic ash released from the Eyjafjallajökull 2010 eruption (Miffre et al., 2011, 2012a, b), ii) desert dust mixed with nondustparticles (Miffre et al., 2011 Dupart et al., 2012), iii) desert dust mixed with sea-salt andbackground spherical particles as an example of a three-component particle mixture (David etal., 2013a). From these field measurements, three main results have been retrieved: (a) Rangere solved particles number ...