Atmospheric processing and aerosol aging responsible for observed increase in absorptivity of long-range-transported smoke over the southeast Atlantic
Abstract. Biomass burning aerosol (BBA) from agricultural fires in southern Africa contributes about one-third of the global carbonaceous aerosol load. These particles have strong radiative effects in the southeast Atlantic (SEA), which depend in part on the radiative contrast between the aerosol layer in the free troposphere (FT) and the underlying cloud layer. However, there is large disagreement in model estimates of aerosol-driven climate forcing due to uncertainties in the vertical distribution, optical properties, and life cycle of these particles. This study applies a novel method combining remote sensing observations with regional model outputs to investigate the aging of the BBA and its impact on the optical properties during transatlantic transport from emission sources in Africa to the SEA. Results show distinct variations in extinction Ångström exponent (EAE) and single-scattering albedo (SSA) as aerosols age. Near the source, fresh aerosols are characterized by low mean SSA (0.84) and high EAE (1.85), indicating smaller, highly absorbing particles. By isolating marine contributions from the total column during BBA transport across the SEA, our analysis reveals an initial decrease in BBA absorptivity, with mean FT SSA of 0.87 after 6–7 d, followed by increased absorptivity with mean FT SSA of 0.84 after 10 d, suggesting enhanced absorption due to chemical aging. These findings indicate that BBA becomes more absorbing during extended transport across the SEA, with implications for reducing model uncertainties. Our remote-sensing-based results agree well with previous in situ studies and offer new insights into aerosol–radiation interactions and the energy balance over the SEA.
Authors
- Ian Chang (ORCID: https://orcid.org/0000-0002-0815-275X)
- Pawan Gupta (ORCID: https://orcid.org/0000-0002-0979-472X)
- Pablo E. Saide (ORCID: https://orcid.org/0000-0002-3879-7962)
- Amie Dobracki (ORCID: https://orcid.org/0000-0002-4895-1716)
- Paquita Zuidema (ORCID: https://orcid.org/0000-0003-4719-372X)
- Arthur J. Sedlacek (ORCID: https://orcid.org/0000-0001-9595-3653)
- Lan Gao (ORCID: https://orcid.org/0000-0002-6607-3240)
- Elena Lind
- Calvin Howes (ORCID: https://orcid.org/0000-0003-0511-7745)
- Abdulamid A. Fakoya (ORCID: https://orcid.org/0000-0002-3926-7410)
- Gregory R. Carmichael (ORCID: https://orcid.org/0000-0001-8097-3475)
- T. F. Eck (ORCID: https://orcid.org/0000-0001-9801-1610)
- Jens Redemann (ORCID: https://orcid.org/0000-0002-2404-7984)
- Connor Flynn (ORCID: https://orcid.org/0000-0002-9182-6531)
- B. N. Holben (ORCID: https://orcid.org/0000-0002-1251-9809)
- Samuel LeBlanc (ORCID: https://orcid.org/0000-0003-0173-3890)
- Gonzalo A. Ferrada (ORCID: https://orcid.org/0000-0001-7502-9439)
- Michal Segal‐Rozenhaimer (ORCID: https://orcid.org/0000-0002-7577-4268)
- Kristina Pistone (ORCID: https://orcid.org/0000-0002-6130-0192)
- Logan Mitchell (ORCID: https://orcid.org/0000-0001-8067-4723)
Institutions
- University of North Carolina at Charlotte (US)
- University of Iowa (US)
- Ames Research Center (US)
- Goddard Space Flight Center (US)
- National Oceanic and Atmospheric Administration (US)
- University of Miami (US)
- University of California, Los Angeles (US)
- Cooperative Institute for Research in Environmental Sciences (US)
- The Aerospace Corporation (US)
- University of Colorado Boulder (US)
- Brookhaven National Laboratory (US)
- NOAA Oceanic and Atmospheric Research (US)
- Sustainability Institute (ZA)
- Bay Area Environmental Research Institute (US)
- University of Maryland, Baltimore County (US)
- University of Oklahoma (US)
Publication Details
- Journal
- Atmospheric chemistry and physics
- Published
- 2025-07-25
- DOI
- https://doi.org/10.5194/acp-25-7879-2025
- Citations
- 2
- Primary Topic
- Atmospheric chemistry and aerosols
- Type
- article
- Field-Weighted Citation Impact
- 2.60