Preprints
https://doi.org/10.5194/acp-2021-1097
https://doi.org/10.5194/acp-2021-1097
 
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18 Jan 2022
18 Jan 2022
Status: a revised version of this preprint was accepted for the journal ACP and is expected to appear here in due course.

Australian wildfire smoke in the stratosphere: the decay phase in 2020/21 and impact on ozone depletion

Kevin Ohneiser1, Albert Ansmann1, Bernd Kaifler2, Alexandra Chudnovsky3, Boris Barja4, Daniel A. Knopf5, Natalie Kaifler2, Holger Baars1, Patric Seifert1, Diego Villanueva1, Cristofer Jimenez1, Martin Radenz1, Ronny Engelmann1, Igor Veselovskii6, and Felix Zamorano4 Kevin Ohneiser et al.
  • 1Leibniz Institute for Tropospheric Research, Leipzig, Germany
  • 2Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
  • 3Tel Aviv University, Porter School of Earth Sciences and Environment, Tel Aviv, Israel
  • 4Atmospheric Research Laboratory, University of Magallanes, Punta Arenas, Chile
  • 5School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794-5000, USA
  • 6Prokhorov General Physics Institute of the Russian Academy of Sciences, Moscow, Russia

Abstract. Record-breaking wildfires raged in southeastern Australia in late December 2019 and early January 2020. Rather strong pyrocumulonimbus (pyroCb) convection developed over the fire areas and lifted enormous amounts of biomass-burning smoke into the tropopause region and caused the strongest wildfire-related stratospheric aerosol perturbation ever observed around the globe. We discuss the geometrical, optical, and microphyscial properties of the stratospheric smoke layers and the decay of this major stratospheric perturbation. A multiwavelength polarization Raman lidar at Punta Arenas (53.2° S, 70.9° W), southern Chile, and an elastic-backscatter Raman lidar at Río Grande (53.8° S, 67.7° W) in southern Argentina were operated to monitor the major record-breaking event until the end of 2021. These lidar measurements can be regarded as representative for mid to high latitudes in the Southern Hemisphere. A unique dynamical feature, an anticyclonic, smoke-filled vortex with 1000 km horizontal width and 5 km vertical extent, which ascended by about 500 m per day, was observed over the full last week of January 2020. The key results of the long-term study are as follows: The smoke layers extended, on average, from 9 to 24 km in height. The smoke partly ascended to more than 30 km height as a result of self-lifting processes. Clear signs of a smoke impact on the record-breaking ozone hole over Antarctica in September–November 2020 were found. A slow decay of the stratospheric perturbation detected by means of the 532 nm aerosol optical thickness (AOT) yielded an e-folding decay time of 19–20 months. The maximum smoke AOT was around 1.0 over Punta Arenas in January 2020 and thus two to three orders of magnitude above the stratospheric aerosol background of 0.005. After two months with strongly varying smoke conditions, the 532 nm AOT decreased to 0.03–0.06 from March–December 2020 and to 0.015–0.03 throughout 2021. The particle extinction coefficients were in the range of 10–75 Mm−1 in January 2020, and later on mostly between 1 and 5 Mm−1. Combined lidar-photometer retrievals revealed typical smoke extinction-to-backscatter ratios of 69 ±19 sr (at 355 nm), 91 ± 17 sr (at 532 nm), and 120 ± 22 sr (at 1064 nm). An ozone reduction of 20–25 % in the 15–22 km height range was observed over Antarctic and New Zealand ozonesonde stations in the smoke-polluted air with particle surface area concentrations of 1–5 μm2 cm−3.

Kevin Ohneiser et al.

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-1097', Anonymous Referee #1, 09 Feb 2022
  • RC2: 'Comment on acp-2021-1097', Anonymous Referee #2, 20 Feb 2022

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-1097', Anonymous Referee #1, 09 Feb 2022
  • RC2: 'Comment on acp-2021-1097', Anonymous Referee #2, 20 Feb 2022

Kevin Ohneiser et al.

Kevin Ohneiser et al.

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Executive editor
Wildfires have attracted increasing attention in recent years because of their effects on local air quality, as well as on regional and global climate. Ohneiser et al. documents with impressive accuracy the appearance of wildfire plumes in the stratosphere over Australia in 2020/2021, showing strong influence on stratospheric ozone. We recommend readers to read this paper together with Solomon et al. ("On the stratospheric chemistry of midlatitude wildfire smoke", PNAS 2022,https://doi.org/10.1073/pnas.2117325119). Both studies highlight the importance of wildfires for stratospheric chemistry and the recovery of the ozone layer in a warming climate.
Short summary
We present and discuss long-term lidar observations of the largest stratospheric perturbation by wildfire smoke ever observed. The smoke originated from the record-breaking Australian fires in 2019–2020 and affect climate conditions and even the ozone layer in the Southern Hemisphere. The obvious link between dense smoke occurrence in the stratosphere and strong ozone depletion found in the Arctic as well as in the Antarctic in 2020 can be regarded as a new aspect of climate change.
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