Phase transition observations and discrimination of small cloud particles by light polarization in expansion chamber experiments

Par Conseil national de recherches du Canada

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DOI	Trouver le DOI : https://doi.org/10.5194/acp-16-3651-2016
Auteur	Rechercher : Nichman, Leonid; Rechercher : Fuchs, Claudia; Rechercher : Järvinen, Emma; Rechercher : Ignatius, Karoliina; Rechercher : Höppel, Niko Florian; Rechercher : Dias, Antonio; Rechercher : Heinritzi, Martin; Rechercher : Simon, Mario; Rechercher : Tröstl, Jasmin; Rechercher : Wagner, Andrea Christine; Rechercher : Wagner, Robert; Rechercher : Williamson, Christina; Rechercher : Yan, Chao; Rechercher : Connolly, Paul James; Rechercher : Dorsey, James Robert; Rechercher : Duplissy, Jonathan; Rechercher : Ehrhart, Sebastian; Rechercher : Frege, Carla; Rechercher : Gordon, Hamish; Rechercher : Hoyle, Christopher Robert; Rechercher : Kristensen, Thomas Bjerring; Rechercher : Steiner, Gerhard; Rechercher : Mcpherson Donahue, Neil; Rechercher : Flagan, Richard; Rechercher : Gallagher, Martin William; Rechercher : Kirkby, Jasper; Rechercher : Möhler, Ottmar; Rechercher : Saathoff, Harald; Rechercher : Schnaiter, Martin; Rechercher : Stratmann, Frank; Rechercher : Tomé, António
Format	Texte, Article
Résumé	Cloud microphysical processes involving the ice phase in tropospheric clouds are among the major uncertainties in cloud formation, weather, and general circulation models. The detection of aerosol particles, liquid droplets, and ice crystals, especially in the small cloud particle-size range below 50 μm, remains challenging in mixed phase, often unstable environments. The Cloud Aerosol Spectrometer with Polarization (CASPOL) is an airborne instrument that has the ability to detect such small cloud particles and measure the variability in polarization state of their backscattered light. Here we operate the versatile Cosmics Leaving OUtdoor Droplets (CLOUD) chamber facility at the European Organization for Nuclear Research (CERN) to produce controlled mixed phase and other clouds by adiabatic expansions in an ultraclean environment, and use the CASPOL to discriminate between different aerosols, water, and ice particles. In this paper, optical property measurements of mixed-phase clouds and viscous secondary organic aerosol (SOA) are presented. We report observations of significant liquid–viscous SOA particle polarization transitions under dry conditions using CASPOL. Cluster analysis techniques were subsequently used to classify different types of particles according to their polarization ratios during phase transition. A classification map is presented for water droplets, organic aerosol (e.g., SOA and oxalic acid), crystalline substances such as ammonium sulfate, and volcanic ash. Finally, we discuss the benefits and limitations of this classification approach for atmospherically relevant concentrations and mixtures with respect to the CLOUD 8–9 campaigns and its potential contribution to tropical troposphere layer analysis.
Date de publication	2016-03-16
Maison d’édition	Copernicus Publications on behalf of the European Geosciences Union
Dans	Atmospheric Chemistry and Physics 16, nº 5 : 3651–3664.
Langue	anglais
Publications évaluées par des pairs	Oui
Publication du CNRC	Cette publication n’est pas du CNRC Ce sont des publications qui ont été rédigées par un auteur du CNRC, mais avant que celui-ci soit employé du CNRC.
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Identificateur de l’enregistrement	8242a715-744b-4256-a562-8b322b26eb1f
Enregistrement créé	2019-10-18
Enregistrement modifié	2020-05-30

Date de modification :: 2024-07-22