The radiative impact of biomass burning aerosols on dust emissions over Namibia and the long-range transport of smoke observed during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) campaign
<p>The radiative effects of biomass burning aerosols (BBAs) on low-level atmospheric circulation over southern Africa are investigated on 5 September 2017 during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) field campaign. This is conducted using a variety of in situ and...
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2024-04-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://acp.copernicus.org/articles/24/4265/2024/acp-24-4265-2024.pdf |
| _version_ | 1797215380998979584 |
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| author | C. Flamant J.-P. Chaboureau M. Gaetani K. Schepanski P. Formenti |
| author_facet | C. Flamant J.-P. Chaboureau M. Gaetani K. Schepanski P. Formenti |
| author_sort | C. Flamant |
| collection | DOAJ |
| description | <p>The radiative effects of biomass burning aerosols (BBAs) on low-level atmospheric circulation over southern Africa are investigated on 5 September 2017 during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) field campaign. This is conducted using a variety of in situ and remote sensing observations, as well as two 5 d ensemble simulations made with the Meso-NH mesoscale model, one including the direct and semi-direct radiative effects of aerosols and one in which these effects are not included. We show that the radiative impact of BBA building up over a period of 5 d in the Meso-NH simulations can lead to significantly different circulations at low and middle levels, thereby affecting dust emissions over southern Namibia and northwestern South Africa as well as the transport of BBA in a so-called “river of smoke”. While most of the regional-scale dynamics, thermodynamics and composition features are convincingly represented in the simulation with BBA radiative effects, neglecting the radiative impact of BBA leads to unrealistic representations of (i) the low-level jet (LLJ) over the plateau, which is the main low-level dynamic feature fostering dust emission, and (ii) the mid-level dynamics pertaining to the transport of BBA from the fire-prone regions in the tropics to the mid-latitudes. For instance, when the BBA radiative impacts are not included, the LLJ is too weak and not well established over night, and the developing convective planetary boundary layer (PBL) is too deep compared to observations. The deeper convective PBL over Etosha and surrounding areas is related to the enhanced anomalous upward motion caused by the eastern displacement of the river of smoke. This eastern displacement is, in turn, related to the weaker southerly African easterly jet. Both ensemble simulations provide clear evidence that the enhanced near-surface extinction coefficient values detected from observations over Etosha are related to the downward mixing of BBA in the developing convective boundary layer rather than dust being emitted as a result of the LLJ breakdown after sunrise. This study suggests that the radiative effect of BBAs needs to be taken into account to properly forecast dust emissions in Namibia.</p> |
| first_indexed | 2024-04-24T11:29:09Z |
| format | Article |
| id | doaj.art-b4e63bd4b1ca483fbe6362106d64aebf |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-04-24T11:29:09Z |
| publishDate | 2024-04-01 |
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| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-b4e63bd4b1ca483fbe6362106d64aebf2024-04-10T11:43:13ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242024-04-01244265428810.5194/acp-24-4265-2024The radiative impact of biomass burning aerosols on dust emissions over Namibia and the long-range transport of smoke observed during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) campaignC. Flamant0J.-P. Chaboureau1M. Gaetani2K. Schepanski3P. Formenti4LATMOS, CNRS, Sorbonne Université, UVSQ, 75252 Paris, FranceLAERO, Université de Toulouse, CNRS, UT3, IRD, 31400 Toulouse, FranceDepartment of Science Technology and Society, Scuola Universitaria Superiore IUSS, Pavia, ItalyInstitute of Meteorology, Freie Universität Berlin, Berlin, GermanyUniversité Paris Cité and Université Paris Est Créteil, CNRS, LISA, 75013 Paris, France<p>The radiative effects of biomass burning aerosols (BBAs) on low-level atmospheric circulation over southern Africa are investigated on 5 September 2017 during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) field campaign. This is conducted using a variety of in situ and remote sensing observations, as well as two 5 d ensemble simulations made with the Meso-NH mesoscale model, one including the direct and semi-direct radiative effects of aerosols and one in which these effects are not included. We show that the radiative impact of BBA building up over a period of 5 d in the Meso-NH simulations can lead to significantly different circulations at low and middle levels, thereby affecting dust emissions over southern Namibia and northwestern South Africa as well as the transport of BBA in a so-called “river of smoke”. While most of the regional-scale dynamics, thermodynamics and composition features are convincingly represented in the simulation with BBA radiative effects, neglecting the radiative impact of BBA leads to unrealistic representations of (i) the low-level jet (LLJ) over the plateau, which is the main low-level dynamic feature fostering dust emission, and (ii) the mid-level dynamics pertaining to the transport of BBA from the fire-prone regions in the tropics to the mid-latitudes. For instance, when the BBA radiative impacts are not included, the LLJ is too weak and not well established over night, and the developing convective planetary boundary layer (PBL) is too deep compared to observations. The deeper convective PBL over Etosha and surrounding areas is related to the enhanced anomalous upward motion caused by the eastern displacement of the river of smoke. This eastern displacement is, in turn, related to the weaker southerly African easterly jet. Both ensemble simulations provide clear evidence that the enhanced near-surface extinction coefficient values detected from observations over Etosha are related to the downward mixing of BBA in the developing convective boundary layer rather than dust being emitted as a result of the LLJ breakdown after sunrise. This study suggests that the radiative effect of BBAs needs to be taken into account to properly forecast dust emissions in Namibia.</p>https://acp.copernicus.org/articles/24/4265/2024/acp-24-4265-2024.pdf |
| spellingShingle | C. Flamant J.-P. Chaboureau M. Gaetani K. Schepanski P. Formenti The radiative impact of biomass burning aerosols on dust emissions over Namibia and the long-range transport of smoke observed during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) campaign Atmospheric Chemistry and Physics |
| title | The radiative impact of biomass burning aerosols on dust emissions over Namibia and the long-range transport of smoke observed during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) campaign |
| title_full | The radiative impact of biomass burning aerosols on dust emissions over Namibia and the long-range transport of smoke observed during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) campaign |
| title_fullStr | The radiative impact of biomass burning aerosols on dust emissions over Namibia and the long-range transport of smoke observed during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) campaign |
| title_full_unstemmed | The radiative impact of biomass burning aerosols on dust emissions over Namibia and the long-range transport of smoke observed during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) campaign |
| title_short | The radiative impact of biomass burning aerosols on dust emissions over Namibia and the long-range transport of smoke observed during the Aerosols, Radiation and Clouds in southern Africa (AEROCLO-sA) campaign |
| title_sort | radiative impact of biomass burning aerosols on dust emissions over namibia and the long range transport of smoke observed during the aerosols radiation and clouds in southern africa aeroclo sa campaign |
| url | https://acp.copernicus.org/articles/24/4265/2024/acp-24-4265-2024.pdf |
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