Radiative impacts of the Australian bushfires 2019–2020 – Part 2: Large-scale and in-vortex radiative heating
<p>Record-breaking wildfires ravaged south-eastern Australia during the fire season 2019–2020. The intensity of the fires reached its paroxysmal phase at the turn of the year 2019–2020, when large pyro-cumulonimbi developed. Pyro-convective activity injected biomass burning aerosols and gases...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2023-12-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/23/15523/2023/acp-23-15523-2023.pdf |
| _version_ | 1797385966474756096 |
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| author | P. Sellitto P. Sellitto R. Belhadji J. Cuesta A. Podglajen B. Legras |
| author_facet | P. Sellitto P. Sellitto R. Belhadji J. Cuesta A. Podglajen B. Legras |
| author_sort | P. Sellitto |
| collection | DOAJ |
| description | <p>Record-breaking wildfires ravaged south-eastern Australia during the fire season 2019–2020. The intensity of the fires reached its paroxysmal phase at the turn of the year 2019–2020, when large pyro-cumulonimbi developed. Pyro-convective activity injected biomass burning aerosols and gases in the upper-troposphere–lower-stratosphere (UTLS), producing a long-lasting perturbation to the atmospheric composition and the stratospheric aerosol layer. The large absorptivity of the biomass burning plume produced self-lofting of the plume and thus modified its vertical dynamics and horizontal dispersion. Another effect of the in-plume absorption was the generation of compact smoke-charged anticyclonic vortices which ascended up to 35 km altitude due to diabatic heating. We use observational and modelling description of this event to isolate the main vortex from the dominant Southern Hemispheric biomass burning aerosol plume. Entering this information into an offline radiative transfer model, and with hypotheses on the absorptivity and the angular scattering properties of the aerosol layer, we estimate the radiative heating rates (HRs) in the plume and the vortex. We found that the hemispheric-scale plume produced a HR of <span class="inline-formula">0.08±0.05</span> K d<span class="inline-formula"><sup>−1</sup></span> (from 0.01 to 0.15 K d<span class="inline-formula"><sup>−1</sup></span>, depending on the assumption on the aerosol optical properties), as a monthly average value for February 2020, which is strongly dependent on the assumptions on the aerosol optical properties and therefore on the plume ageing. We also found in-vortex HRs as large as 15–20 K d<span class="inline-formula"><sup>−1</sup></span> in the denser sections of the main vortex (<span class="inline-formula">8.4±6.1</span> K d<span class="inline-formula"><sup>−1</sup></span> on average in the vortex). Our results suggest that radiatively heated ascending isolated vortices are likely dominated by small-sized strongly absorbing black carbon particles. The hemispheric-scale and in-vortex HR estimates are consistent with the observed ensemble self-lofting (a few kilometres in 4 months) and the main isolated vortex rise (<span class="inline-formula">∼</span> 20 km in 2 months). Our results also show evidence of the importance of longwave emission in the net HR of biomass burning plumes.</p> |
| first_indexed | 2024-03-08T22:02:02Z |
| format | Article |
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| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-03-08T22:02:02Z |
| publishDate | 2023-12-01 |
| publisher | Copernicus Publications |
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| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-4bd5dd4556e541d3bcce4c6a7def72922023-12-19T11:35:15ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242023-12-0123155231553510.5194/acp-23-15523-2023Radiative impacts of the Australian bushfires 2019–2020 – Part 2: Large-scale and in-vortex radiative heatingP. Sellitto0P. Sellitto1R. Belhadji2J. Cuesta3A. Podglajen4B. Legras5Univ. Paris Est Créteil and Université de Paris, CNRS, Laboratoire Interuniversitaire des Systèmes Atmosphériques, Institut Pierre Simon Laplace, Créteil, FranceIstituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo, Catania, ItalyUniv. Paris Est Créteil and Université de Paris, CNRS, Laboratoire Interuniversitaire des Systèmes Atmosphériques, Institut Pierre Simon Laplace, Créteil, FranceUniv. Paris Est Créteil and Université de Paris, CNRS, Laboratoire Interuniversitaire des Systèmes Atmosphériques, Institut Pierre Simon Laplace, Créteil, FranceLaboratoire de Météorologie Dynamique, UMR CNRS 8539, École Normale Supérieure, PSL Research University, École Polytechnique, Sorbonne Universités, École des Ponts PARISTECH, Institut Pierre Simon Laplace, Paris, FranceLaboratoire de Météorologie Dynamique, UMR CNRS 8539, École Normale Supérieure, PSL Research University, École Polytechnique, Sorbonne Universités, École des Ponts PARISTECH, Institut Pierre Simon Laplace, Paris, France<p>Record-breaking wildfires ravaged south-eastern Australia during the fire season 2019–2020. The intensity of the fires reached its paroxysmal phase at the turn of the year 2019–2020, when large pyro-cumulonimbi developed. Pyro-convective activity injected biomass burning aerosols and gases in the upper-troposphere–lower-stratosphere (UTLS), producing a long-lasting perturbation to the atmospheric composition and the stratospheric aerosol layer. The large absorptivity of the biomass burning plume produced self-lofting of the plume and thus modified its vertical dynamics and horizontal dispersion. Another effect of the in-plume absorption was the generation of compact smoke-charged anticyclonic vortices which ascended up to 35 km altitude due to diabatic heating. We use observational and modelling description of this event to isolate the main vortex from the dominant Southern Hemispheric biomass burning aerosol plume. Entering this information into an offline radiative transfer model, and with hypotheses on the absorptivity and the angular scattering properties of the aerosol layer, we estimate the radiative heating rates (HRs) in the plume and the vortex. We found that the hemispheric-scale plume produced a HR of <span class="inline-formula">0.08±0.05</span> K d<span class="inline-formula"><sup>−1</sup></span> (from 0.01 to 0.15 K d<span class="inline-formula"><sup>−1</sup></span>, depending on the assumption on the aerosol optical properties), as a monthly average value for February 2020, which is strongly dependent on the assumptions on the aerosol optical properties and therefore on the plume ageing. We also found in-vortex HRs as large as 15–20 K d<span class="inline-formula"><sup>−1</sup></span> in the denser sections of the main vortex (<span class="inline-formula">8.4±6.1</span> K d<span class="inline-formula"><sup>−1</sup></span> on average in the vortex). Our results suggest that radiatively heated ascending isolated vortices are likely dominated by small-sized strongly absorbing black carbon particles. The hemispheric-scale and in-vortex HR estimates are consistent with the observed ensemble self-lofting (a few kilometres in 4 months) and the main isolated vortex rise (<span class="inline-formula">∼</span> 20 km in 2 months). Our results also show evidence of the importance of longwave emission in the net HR of biomass burning plumes.</p>https://acp.copernicus.org/articles/23/15523/2023/acp-23-15523-2023.pdf |
| spellingShingle | P. Sellitto P. Sellitto R. Belhadji J. Cuesta A. Podglajen B. Legras Radiative impacts of the Australian bushfires 2019–2020 – Part 2: Large-scale and in-vortex radiative heating Atmospheric Chemistry and Physics |
| title | Radiative impacts of the Australian bushfires 2019–2020 – Part 2: Large-scale and in-vortex radiative heating |
| title_full | Radiative impacts of the Australian bushfires 2019–2020 – Part 2: Large-scale and in-vortex radiative heating |
| title_fullStr | Radiative impacts of the Australian bushfires 2019–2020 – Part 2: Large-scale and in-vortex radiative heating |
| title_full_unstemmed | Radiative impacts of the Australian bushfires 2019–2020 – Part 2: Large-scale and in-vortex radiative heating |
| title_short | Radiative impacts of the Australian bushfires 2019–2020 – Part 2: Large-scale and in-vortex radiative heating |
| title_sort | radiative impacts of the australian bushfires 2019 2020 part 2 large scale and in vortex radiative heating |
| url | https://acp.copernicus.org/articles/23/15523/2023/acp-23-15523-2023.pdf |
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