How the extreme 2019–2020 Australian wildfires affected global circulation and adjustments
Wildfires are a significant source of absorbing aerosols in the atmosphere. Extreme fires in particular, such as those during the 2019–2020 Australian wildfire season (Black Summer fires), can have considerable large-scale effects. In this context, the climate impact of extreme wildfires unfolds not...
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ftcopernicus:oai:publications.copernicus.org:acp109219 2023-09-05T13:23:31+02:00 How the extreme 2019–2020 Australian wildfires affected global circulation and adjustments Senf, Fabian Heinold, Bernd Kubin, Anne Müller, Jason Schrödner, Roland Tegen, Ina 2023-08-11 application/pdf https://doi.org/10.5194/acp-23-8939-2023 https://acp.copernicus.org/articles/23/8939/2023/ eng eng doi:10.5194/acp-23-8939-2023 https://acp.copernicus.org/articles/23/8939/2023/ eISSN: 1680-7324 Text 2023 ftcopernicus https://doi.org/10.5194/acp-23-8939-2023 2023-08-14T16:24:19Z Wildfires are a significant source of absorbing aerosols in the atmosphere. Extreme fires in particular, such as those during the 2019–2020 Australian wildfire season (Black Summer fires), can have considerable large-scale effects. In this context, the climate impact of extreme wildfires unfolds not only because of the emitted carbon dioxide but also due to smoke aerosol released up to an altitude of 17 km. The overall aerosol effects depend on a variety of factors, such as the amount emitted, the injection height, and the composition of the burned material, and is therefore subject to considerable uncertainty. In the present study, we address the global impact caused by the exceptionally strong and high-reaching smoke emissions from the Australian wildfires using simulations with a global aerosol–climate model. We show that the absorption of solar radiation by the black carbon contained in the emitted smoke led to a shortwave radiative forcing of more than +5 W m −2 in the southern mid-latitudes of the lower stratosphere. Subsequent adjustment processes in the stratosphere slowed down the diabatically driven meridional circulation, thus redistributing the heating perturbation on a global scale. As a result of these stratospheric adjustments, a positive temperature perturbation developed in both hemispheres, leading to additional longwave radiation emitted back to space. According to the model results, this adjustment occurred in the stratosphere within the first 2 months after the event. At the top of the atmosphere (TOA), the net effective radiative forcing (ERF) averaged over the Southern Hemisphere was initially dominated by the instantaneous positive radiative forcing of about +0.5 W m −2 , for which the positive sign resulted mainly from the presence of clouds above the Southern Ocean. The longwave adjustments led to a compensation of the initially net positive TOA ERF, which is seen in the Southern Hemisphere, the tropics, and the northern mid-latitudes. The simulated changes in the lower stratosphere ... Text Southern Ocean Copernicus Publications: E-Journals Southern Ocean Atmospheric Chemistry and Physics 23 15 8939 8958 |
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English |
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Wildfires are a significant source of absorbing aerosols in the atmosphere. Extreme fires in particular, such as those during the 2019–2020 Australian wildfire season (Black Summer fires), can have considerable large-scale effects. In this context, the climate impact of extreme wildfires unfolds not only because of the emitted carbon dioxide but also due to smoke aerosol released up to an altitude of 17 km. The overall aerosol effects depend on a variety of factors, such as the amount emitted, the injection height, and the composition of the burned material, and is therefore subject to considerable uncertainty. In the present study, we address the global impact caused by the exceptionally strong and high-reaching smoke emissions from the Australian wildfires using simulations with a global aerosol–climate model. We show that the absorption of solar radiation by the black carbon contained in the emitted smoke led to a shortwave radiative forcing of more than +5 W m −2 in the southern mid-latitudes of the lower stratosphere. Subsequent adjustment processes in the stratosphere slowed down the diabatically driven meridional circulation, thus redistributing the heating perturbation on a global scale. As a result of these stratospheric adjustments, a positive temperature perturbation developed in both hemispheres, leading to additional longwave radiation emitted back to space. According to the model results, this adjustment occurred in the stratosphere within the first 2 months after the event. At the top of the atmosphere (TOA), the net effective radiative forcing (ERF) averaged over the Southern Hemisphere was initially dominated by the instantaneous positive radiative forcing of about +0.5 W m −2 , for which the positive sign resulted mainly from the presence of clouds above the Southern Ocean. The longwave adjustments led to a compensation of the initially net positive TOA ERF, which is seen in the Southern Hemisphere, the tropics, and the northern mid-latitudes. The simulated changes in the lower stratosphere ... |
format |
Text |
author |
Senf, Fabian Heinold, Bernd Kubin, Anne Müller, Jason Schrödner, Roland Tegen, Ina |
spellingShingle |
Senf, Fabian Heinold, Bernd Kubin, Anne Müller, Jason Schrödner, Roland Tegen, Ina How the extreme 2019–2020 Australian wildfires affected global circulation and adjustments |
author_facet |
Senf, Fabian Heinold, Bernd Kubin, Anne Müller, Jason Schrödner, Roland Tegen, Ina |
author_sort |
Senf, Fabian |
title |
How the extreme 2019–2020 Australian wildfires affected global circulation and adjustments |
title_short |
How the extreme 2019–2020 Australian wildfires affected global circulation and adjustments |
title_full |
How the extreme 2019–2020 Australian wildfires affected global circulation and adjustments |
title_fullStr |
How the extreme 2019–2020 Australian wildfires affected global circulation and adjustments |
title_full_unstemmed |
How the extreme 2019–2020 Australian wildfires affected global circulation and adjustments |
title_sort |
how the extreme 2019–2020 australian wildfires affected global circulation and adjustments |
publishDate |
2023 |
url |
https://doi.org/10.5194/acp-23-8939-2023 https://acp.copernicus.org/articles/23/8939/2023/ |
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Southern Ocean |
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Southern Ocean |
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Southern Ocean |
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Southern Ocean |
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eISSN: 1680-7324 |
op_relation |
doi:10.5194/acp-23-8939-2023 https://acp.copernicus.org/articles/23/8939/2023/ |
op_doi |
https://doi.org/10.5194/acp-23-8939-2023 |
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Atmospheric Chemistry and Physics |
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23 |
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15 |
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8939 |
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8958 |
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