The Ascension Island Boundary Layer in the Remote Southeast Atlantic is Often Smoky

Paquita Zuidema, Arthur J. Sedlacek, Connor Flynn, Stephen Springston, Rodrigo Delgadillo, Jianhao Zhang, Allison C. Aiken, Annette Koontz, Paytsar Muradyan

Research output: Contribution to journalArticle

27 Scopus citations

Abstract

Observations from June to October 2016, from a surface-based ARM Mobile Facility deployment on Ascension Island (8°S, 14.5°W) indicate that refractory black carbon (rBC) is almost always present within the boundary layer. The rBC mass concentrations, light absorption coefficients, and cloud condensation nuclei concentrations vary in concert and synoptically, peaking in August. Light absorption coefficients at three visible wavelengths as a function of rBC mass are approximately double that calculated from black carbon in lab studies. A spectrally-flat absorption angstrom exponent suggests most of the light absorption is from lens-coated black carbon. The single-scattering-albedo increases systematically from August to October in both 2016 and 2017, with monthly means of 0.78 ± 0.02 (August), 0.81 ± 0.03 (September), and 0.83 ± 0.03 (October) at the green wavelength. Boundary layer aerosol loadings are only loosely correlated with total aerosol optical depth, with smoke more likely to be present in the boundary layer earlier in the biomass burning season, evolving to smoke predominantly present above the cloud layers in September–October, typically resting upon the cloud top inversion. The time period with the campaign-maximum near-surface light absorption and column aerosol optical depth, on 13–16 August 2016, is investigated further. Backtrajectories that indicate more direct boundary layer transport westward from the African continent is central to explaining the elevated surface aerosol loadings.

Original languageEnglish (US)
Pages (from-to)4456-4465
Number of pages10
JournalGeophysical Research Letters
Volume45
Issue number9
DOIs
StatePublished - May 16 2018

Keywords

  • DOE AMF1
  • absorbing aerosol
  • remote southeast Atlantic
  • smoke

ASJC Scopus subject areas

  • Geophysics
  • Earth and Planetary Sciences(all)

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    Zuidema, P., Sedlacek, A. J., Flynn, C., Springston, S., Delgadillo, R., Zhang, J., Aiken, A. C., Koontz, A., & Muradyan, P. (2018). The Ascension Island Boundary Layer in the Remote Southeast Atlantic is Often Smoky. Geophysical Research Letters, 45(9), 4456-4465. https://doi.org/10.1002/2017GL076926