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© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 18 Jul 2019

Submitted as: research article | 18 Jul 2019

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This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Atmospheric Chemistry and Physics (ACP) and is expected to appear here in due course.

The unprecedented 2017–2018 stratospheric smoke event: Decay phase and aerosol properties observed with EARLINET

Holger Baars1, Albert Ansmann1, Kevin Ohneiser1, Moritz Haarig1, Ronny Engelmann1, Dietrich Althausen1, Ingrid Hanssen2, Michael Gausa2, Aleksander Pietruczuk3, Artur Szkop3, Iwona S. Stachlewska4, Dongxiang Wang4, Jens Reichhardt5, Annett Skupin1, Ina Mattis6, Thomas Trickl7, Hannes Vogelmann7, Francisco Navas-Guzmán8, Alexander Haefele8, Karen Acheson9, Albert A. Ruth9, Boyan Tatarov10, Detlef Müller10, Qiaoyun Hu11, Thierry Podvin11, Philippe Goloub11, Igor Vesselovski12, Christophe Pietras13, Martial Haeffelin13, Patrick Fréville14, Michaël Sicard15,16, Adolfo Comerón15, Alfonso Javier Fernández García17, Francisco Molero Menéndez17, Carmen Córdoba-Jabonero18, Juan Luis Guerrero-Rascado19, Lucas Alados-Arboledas19, Daniele Bortoli20,21, Maria João Costa20, Davide Dionisi22, Gian Luigi Liberti22, Xuan Wang23, Alessia Sannino24, Nikolaos Papagiannopoulos25, Antonella Boselli25, Lucia Mona25, Giuseppe D'Amico25, Salvatore Romano26, Maria Rita Perrone26, Livio Belegante27, Doina Nicolae27, Ivan Grigorov28, Anna Gialitaki29, Vassilis Amiridis29, Ourania Soupiona30, Alexandros Papayannis30, Rodanthi-Elisaveth Mamouri31, Argyro Nisantzi31, Birgit Heese1, Julian Hofer1, Yoav Y. Schechner32, Ulla Wandinger1, and Gelsomina Pappalardo25 Holger Baars et al.
  • 1Leibniz Institute for Tropospheric Research, Leipzig, Germany
  • 2Andøya Space Center, Andenes, Norway
  • 3Institute of Geophysics, Polish Academy of Sciences, Warsaw, Poland
  • 4Faculty of Physics, University of Warsaw, Warsaw, Poland
  • 5The Lindenberg Meteorological Observatory, Deutscher Wetterdienst, Tauche, Germany
  • 6Meteorological Observatory Hohenpeissenberg, Deutscher Wetterdienst, Hohenpeissenberg, Germany
  • 7IMK-IFU, Karlsruhe Institute of Technology, Garmisch-Partenkirchen, Germany
  • 8Federal Office of Meteorology and Climatology, MeteoSwiss, Payerne, Switzerland
  • 9Physics Department & Environmental Research Institute, University College Cork, Cork, Ireland
  • 10School of Physics, Astronomy and Mathematics, University of Hertfordshire, Hatfield, United Kingdom
  • 11LOA, Université de Lille, Lille, France
  • 12Physics Instrumentation Center of General Physics Institute, Moscow, Russia
  • 13Laboratoire Meteorologie Dinamique, École Polytechnique, Palaiseau, France
  • 14Observatoire de Physique du Globe, Laboratoire de Météorologie Physique, Clermont-Ferrand, France
  • 15CommSensLab, Dept. of Signal Theory and Communications, Universitat Politècnica de Catalunya, Barcelona, Spain
  • 16CTE-CRAE/IEEC,Universitat Politècnica de Catalunya, Barcelona, Spain
  • 17Centrode Investigaciones Energéticas, Medioambientales y Tecnológicas, Department of Environment, Madrid, Spain
  • 18Instituto Nacional de Tècnica Aeroespacial, Atmospheric Research and Instrument. Branch,El Arenosillo/Huelva, Spain
  • 19Andalusian Institute for Earth System Research and University of Granada, Granada, Spain
  • 20Instituto Ciências da Terra, Universidade de Évora, Evora, Portugal
  • 21Departamento de Física, Universidade de Évora, Evora, Portugal
  • 22Consiglio Nazionale delle Ricerche, Istituto di Scienze Marine, Rome-Tor Vergata, Italy
  • 23Consiglio Nazionale delle Ricerche, Istituto Superconduttori, Materiali Innovativie Dispositivi, Naples, Italy
  • 24Dipartimento di Fisica, Università degli studi di Napoli Federico II, Naples, Italy
  • 25Consiglio Nazionaledelle Ricerche, Istituto di Metodologie per l’Analisi Ambientale, Potenza, Italy
  • 26Consorzio Nazionale Interuniversitario per le Scienze Fisichedella Materia and Università del Salento, Lecce, Italy
  • 27National Institute of Research and Development for Optoelectronics, Magurele, Ilfov, Romania
  • 28Institute of Electronics, Bulgarian Academy of Sciences, Sofia, Bulgaria
  • 29IAASARS, National Observatory of Athens, Athens, Greece
  • 30Laser Remote Sensing Unit (LRSU), Physics Department, National Technical University of Athens, Zografou, Greece
  • 31Department of Civil Engineering and Geomatics, Cyprus University of Technology, Limassol, Cyprus
  • 32Faculty of Electrical Engineering, Technion - Israel Institute of Technology, Haifa, Israel

Abstract. Six months of stratospheric aerosol observations with the European Aerosol Research Lidar Network (EARLINET) from August 2017 to January 2018 are presented. The decay phase of an unprecedented, record-breaking stratospheric perturbation caused by wild fire smoke is reported and discussed in terms of geometrical, optical, and microphysical aerosol properties. Enormous amounts of smoke (mainly soot particles) were injected into the upper troposphere and lower stratosphere over fire areas in western Canada on 12 August 2017 during strong thunderstorm-pyrocumulonimbus activity. The stratospheric smoke plumes spread over the entire northern hemisphere in the following weeks and months. Twenty-eight European lidar stations from northern Norway to southern Portugal and the Eastern Mediterranean monitored the strong stratospheric perturbation on a continental scale. The main smoke layer (over central, western, southern, and eastern Europe) was found between 15 and 20 km height since September 2017 (about two weeks after entering the stratosphere). Thin layers of smoke were detected to ascent to 22–24 km height. The stratospheric aerosol optical thickness at 532 nm decreased from values > 0.25 on 21–23 August 2017 to 0.005–0.03 until 5–10 September, and was mainly 0.003–0.004 from October to December 2017, and thus still significantly above the stratospheric background (0.001–0.002). Stratospheric particle extinction coefficients (532 nm) were as high as 50–200 Mm−1 until the beginning of September and of the order of 1 Mm−1 (0.5–5 Mm−1) from October 2017 until the end of January 2018. The corresponding layer mean particle mass concentration was of the order of 0.05–0.5 μg cm−3 over the months. Soot is an efficient ice-nucleating particle (INP) at upper tropospheric (cirrus) temperatures and available to influence cirrus formation when entering the tropopause from above. We estimated INP concentrations of 50–500 L−1 until the first days in September and afterwards 5–50 L−1 until the end of the year 2018 in the lower stratosphere for typical cirrus formation temperatures of −55 °C and ice supersaturation values of 1.15. The measured profiles of the particle linear depolarization rato indicated the predominance of non-spherical soot particles. The 532 nm depolarization ratio decreased with time in the main smoke layer from values of 0.15–0.25 (August–September) to values of 0.05–0.10 (October–November) and < 0.05 (December–January). The decrease of the depolarization ratio is consistent with the steady removal of the larger smoke particles by gravitational settling and changes in the particle shape with time towards a spherical form. An ascending layer with a vertical depth of 500–1000 m was detected (over the Eastern Mediterranean at 32–35° N) that ascended from about 18–19 km to 22–23 km height from the beginning of October to the beginning of December 2017 (about 2 km per month) and may be related to the increasing build up of the winter-hemispheric Brewer–Dobson circulation system.

Holger Baars et al.
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Status: closed
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Holger Baars et al.
Holger Baars et al.
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