Is the near-spherical shape the "new black" for smoke?

• Main Authors: Gialitaki, Anna, Tsekeri, Alexandra, Amiridis, Vassilis, Ceolato, Romain, Paulien, Lucas, Kampouri, Anna, Gkikas, Antonis, Solomos, Stavros, Marinou, Eleni, Haarig, Moritz, Baars, Holger, Ansmann, Albert, Lapyonok, Tatyana, Lopatin, Anton, Dubovik, Oleg, Groß, Silke, Wirth, Martin, Tsichla, Maria, Tsikoudi, Ioanna, Balis, Dimitris
• Other Authors: National Observatory of Athens (NOA), Laboratory of Atmospheric Physics Thessaloniki, Aristotle University of Thessaloniki, ONERA / DOTA, Université de Toulouse Toulouse, ONERA-PRES Université de Toulouse, Department of Meteorology and Climatology Thessaloniki, Research Centre for Atmospheric Physics and Climatology Athens, Academy of Athens, DLR Institut für Physik der Atmosphäre (IPA), Deutsches Zentrum für Luft- und Raumfahrt Oberpfaffenhofen-Wessling (DLR), Leibniz Institute for Tropospheric Research (TROPOS), Laboratoire d’Optique Atmosphérique - UMR 8518 (LOA), Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lille-Centre National de la Recherche Scientifique (CNRS), GRASP-SAS, Remote Sensing Developments, Environmental Chemical Processes Laboratory Heraklion (ECPL), Department of Chemistry Heraklion, University of Crete Heraklion (UOC)-University of Crete Heraklion (UOC), Department of Environmental Physics and Meteorology Zografou campus, Faculty of Physics Zografou campus, National and Kapodistrian University of Athens (NKUA)-National and Kapodistrian University of Athens (NKUA)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2020
• Subjects: Soot; Lidar; Depolarization; Polarization; Smoke; Suies; Particle Linear Depolarization Ratio - PLDR; Fumées; [SPI]Engineering Sciences [physics]; [PHYS]Physics [physics]; Canada; Aerosol Robotic Network
• Online Access: https://hal.archives-ouvertes.fr/hal-02776682; https://hal.archives-ouvertes.fr/hal-02776682v2/document; https://hal.archives-ouvertes.fr/hal-02776682v2/file/DOTA20071.1588080828.pdf; https://doi.org/10.5194/acp-2020-22

International audience We examine the capability of near-spherical-shaped particles to reproduce the triple-wavelength particle linear depolarization ratio (PLDR) and lidar ratio (LR) values measured over Europe for stratospheric smoke originating from Canadian wildfires. The smoke layers were detected both in the troposphere and the stratosphere, though in the latter case the particles presented PLDR values of almost 18 % at 532 nm as well as a strong spectral dependence from the UV to the near-IR wavelength. Although recent simulation studies of rather complicated smoke particle morphologies have shown that heavily coated smoke aggregates can produce large PLDR, herein we propose a much simpler model of compact near-spherical smoke particles. This assumption allows for the reproduction of the observed intensive optical properties of stratospheric smoke, as well as their spectral dependence. We further examine whether an extension of the current Aerosol Robotic Network (AERONET) scattering model to include the near-spherical shapes could be of benefit to the AERONET retrieval for stratospheric smoke cases associated with enhanced PLDR. Results of our study illustrate the fact that triple-wavelength PLDR and LR lidar measurements can provide us with additional insight when it comes to particle characterization. Nous examinons la capacité des particules de forme quasi-sphérique à reproduire le PLDR (Particle Linear Depolarization Ratio) mesurées en Europe pour la fumée stratosphérique provenant des incendies de forêt au Canada. Des couches de fumée ont été détectées à la fois dans la troposphère et la stratosphère, bien que dans ce dernier cas, les particules présentaient des valeurs PLDR de près de 18% à 532 nm ainsi qu'une forte dépendance spectrale de l'UV à proche infrarouge. L'hypothèse selon laquelle les particules de fumée ont une forme presque sphérique permet la reproduction du PLDR et du rapport Lidar (LR) observés, alors que 20% n'était pas possible lors de l'utilisation de formes plus compliquées. ...