Preprints
https://doi.org/10.5194/acp-2021-414
https://doi.org/10.5194/acp-2021-414

  25 May 2021

25 May 2021

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

Observations of Supermicron-Sized Aerosols Originating from Biomass Burning in South Central Africa

Rose Marie Miller1, Greg M. McFarquhar2,3, Robert M. Rauber1, Joseph R. O'Brien4, Siddhant Gupta2,3, Michal Segal-Rozenhaimer5,6, Amie N. Dobracki7, Arthur J. Sedlacek8, Sharon P. Burton9, Steven G. Howell10, Steffen Freitag10, and Caroline Dang11 Rose Marie Miller et al.
  • 1Department of Atmospheric Science, University of Illinois Champaign-Urbana, Urbana, IL, USA
  • 2Cooperative Institute of Mesoscale Meteorological Studies, University of Oklahoma, Norman, OK, USA
  • 3School of Meteorology, University of Oklahoma, OK, USA
  • 4Department of Atmospheric Science, University of North Dakota, Grand Forks, ND, USA
  • 5Bay Area Environmental Research Institute/NASA Ames Research Center, Moffett Field, CA, USA
  • 6Department of Geophysics, Porter school of Environmental and Earth Science, Tel-Aviv University, Tel-Aviv, Israel
  • 7Department of Atmospheric Sciences, Rosenstiel School of Marine and Atmospheric Science, University of Miami, Miami, FL, USA
  • 8Department of Environmental & Climate Sciences, Brookhaven National Laboratory, Upton, NY, USA
  • 9NASA Langley Research Center, Hampton, VA, USA
  • 10Department of Oceanography, University of Hawaii at Manoa, Honolulu, HI, USA
  • 11Universities Space Research Association/NASA Ames Research Center, Moffett Field, CA, USA

Abstract. During the three years of the ObseRvations of Aerosols above CLouds and their intEractionS (ORACLES) campaign, the NASA Orion P-3 was equipped with a 2D-Stereo (2D-S) probe that imaged particles with maximum dimension (D) ranging from 10 < D < 1280 µm. The 2D-S recorded supermicron-sized aerosol particles (SAPs) outside of clouds within biomass burning plumes during flights over the Southeast Atlantic off Africa’s coast. Numerous SAPs with 10 < D < 1520 µm were observed in 2017 and 2018 at altitudes between 1230 m and 3500 m, 1000 km from the coastline mostly between 7–11° S. No SAPs were observed in 2016 as flights were conducted further south and further from the coastline. Number concentrations of black carbon (rBC) measured by a single particle soot photometer ranged from 200 to 1200 cm−3 when SAPs were observed. Transmission electron microscopy images of submicron particulates, collected on Holey carbon grid filters, revealed particles with potassium salts, black carbon and organics while energy-dispersive X-ray spectroscopy spectra detected potassium, a tracer for biomass burning, indicating that the submicron particles originated from biomass burning in addition to black carbon. NOAA Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) three-day back trajectories show a source in northern Angola for times when large SAPs were observed. Fire Information for Resource Management System Moderate Resolution Imaging Spectroradiometer (MODIS) 6 active fire maps showed extensive biomass burning at these locations. Given the back trajectories, the high number concentrations of rBC, and the presence of elemental tracers indicative of biomass burning, it is hypothesized that the SAPs imaged by the 2D-S are examples of unburned plant material previously seen in biomass burning smoke close to the source.

Rose Marie Miller et al.

Status: open (until 20 Jul 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-414', Anonymous Referee #1, 11 Jun 2021 reply

Rose Marie Miller et al.

Rose Marie Miller et al.

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Short summary
A large stratocumulus cloud deck resides off the west coast of central Africa. Biomass burning in Africa produces a large plume of aerosol that is carried by the wind over this stratocumulus cloud deck. This paper shows that particles with sizes from 0.01 to 1 mm reside within this plume. Past studies have shown that biomass burning produces such particles, but this is the first study to show that they can be transported long distances westward over the Atlantic stratocumulus cloud deck.
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