Preprints
https://doi.org/10.5194/acp-2021-862
https://doi.org/10.5194/acp-2021-862

  11 Nov 2021

11 Nov 2021

Review status: this preprint is currently under review for the journal ACP.

Important role of stratospheric injection height for the distribution and radiative forcing of smoke aerosol from the 2019/2020 Australian wildfires

Bernd Heinold1, Holger Baars1, Boris Barja2, Matthew Christensen3,a, Anne Kubin1, Kevin Ohneiser1, Kerstin Schepanski1,b, Nick Schutgens4, Fabian Senf1, Roland Schrödner1, Diego Villanueva1,c, and Ina Tegen1 Bernd Heinold et al.
  • 1Leibniz Institute for Tropospheric Research, Permoserstr. 15, 04318 Leipzig, Germany
  • 2Department of Mathematics and Physics, University of Magallanes, Avenida Bulnes 01855 Punta Arenas, Chile
  • 3Atmospheric, Oceanic and Planetary Physics, University of Oxford, Oxford OX1 3PU, United Kingdom
  • 4Department of Earth Science, Vrije Universiteit Amsterdam, 1081 HV Amsterdam, the Netherlands
  • anow at: Atmospheric Sciences and Global Change Division, Pacific Northwest National Laboratory, Richland, WA, 99352, USA
  • bnow at: Institute of Meteorology, Freie Universität Berlin, Carl-Heinrich-Becker-Weg 6-10, 12165 Berlin, Germany
  • cnow at: Leipzig Institute for Meteorology, University of Leipzig, Germany

Abstract. More than 1 Tg smoke aerosol was emitted into the atmosphere by the exceptional 2019–2020 Southeast Australian wildfires. Triggered by the extreme fire heat, several deep pyroconvective events carried the smoke directly into the stratosphere. Once there, smoke aerosol remained airborne considerably longer than in lower atmospheric layers. The thick plumes traveled eastward thereby being distributed across the high and mid-latitude Southern Hemisphere enhancing the atmospheric opacity. Due to the increased atmospheric lifetime of the smoke plume its radiative effect increased compared to smoke that remains lower altitudes. Global models describing aerosol-climate impacts show significant uncertainties regarding the emission height of aerosols from intense wildfires. Here, we demonstrate by combination of aerosol-climate modeling and lidar observations the importance of the representation of those high-altitude fire smoke layers for estimating the atmospheric energy budget. In this observation-based approach, the Australian wildfire emissions by pyroconvection are explicitly prescribed to the lower stratosphere in different scenarios. The 2019–2020 Australian fires caused a significant top-of-atmosphere hemispheric instantaneous direct radiative forcing signal that reached a magnitude comparable to the radiative forcing induced by anthropogenic absorbing aerosol. Up to +0.50 W m−2 instantaneous direct radiative forcing was modeled at top of the atmosphere, averaged for the Southern Hemisphere for January to March 2020 under all-sky conditions. While at the surface, an instantaneous solar radiative forcing of up to −0.81 W m−2 was found for clear-sky conditions, depending on the model configuration. Since extreme wildfires are expected to occur more frequently in the rapidly changing climate, our findings suggest that deep wildfire plumes must be adequately considered in climate projections in order to obtain reasonable estimates of atmospheric energy budget changes.

Bernd Heinold et al.

Status: open (until 23 Dec 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-862, valuable contribution but some inconsistencies', Anonymous Referee #1, 25 Nov 2021 reply

Bernd Heinold et al.

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The chemistry–climate model ECHAM6.3-HAM2.3-MOZ1.0 HAMMOZ community https://redmine.hammoz.ethz.ch

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Chemistry–climate model ECHAM6.3-HAM2.3-MOZ1.0 The HAMMOZ community https://redmine.hammoz.ethz.ch

Bernd Heinold et al.

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Short summary
The extreme 2019–2020 Australian wildfires produced massive smoke plumes lifted into the lower stratosphere by pyrocumulonimbus convection. Most climate models do not adequately simulate the injection height of such intense fires. This study shows by combination of aerosol-climate modeling with prescribed pyroconvective smoke injection and lidar observations the importance of the representation of most extreme wildfire events for estimating the atmospheric energy budget.
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