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Title: The Ascension Island boundary layer in the remote southeast Atlantic is often smoky

Abstract

Observations from June through 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. 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 indirectly indicate the presence of other light-absorbing aerosols (e.g., brown carbon), most pronounced in June. 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 of 2016, is investigated further. Also, backtrajectories indicate more direct boundary layer transport westward from the African continent is central to explaining the elevated surface aerosol loadings.

Authors:
ORCiD logo [1]; ORCiD logo [2]; ORCiD logo [3];  [2]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [4];  [3];  [5]
  1. Univ. of Miami, Miami, FL (United States). Rosenstiel School of Marine and Atmospheric Sciences
  2. Brookhaven National Lab. (BNL), Upton, NY (United States)
  3. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  4. Los Alamos National Laboratory, Los Alamos NM USA
  5. Argonne National Lab. (ANL), Argonne, IL (United States)
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States); Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Argonne National Lab. (ANL), Argonne, IL (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division; National Aeronautic and Space Administration (NASA)-Aerosol Robotic Network (AERONET)
OSTI Identifier:
1433942
Alternate Identifier(s):
OSTI ID: 1466325; OSTI ID: 1542854
Report Number(s):
BNL-203504-2018-JAAM; LA-UR-19-22760
Journal ID: ISSN 0094-8276
Grant/Contract Number:  
SC0012704; SC0013720; AC02-06CH11357; 89233218CNA000001
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Geophysical Research Letters
Additional Journal Information:
Journal Volume: 45; Journal Issue: 9; Journal ID: ISSN 0094-8276
Publisher:
American Geophysical Union
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; 47 OTHER INSTRUMENTATION; Earth Sciences; aerosol, atmospheric radiation, absorbing aerosols, field measurements, Aerosol optical Depth, absorption angstrom exponent

Citation Formats

Zuidema, Paquita, Sedlacek III, Arthur J., Flynn, Connor, Springston, Stephen, Delgadillo, Rodrigo, Zhang, Jianhao, Aiken, Allison C., Koontz, Annette, and Muradyan, Paytsar. The Ascension Island boundary layer in the remote southeast Atlantic is often smoky. United States: N. p., 2018. Web. doi:10.1002/2017GL076926.
Zuidema, Paquita, Sedlacek III, Arthur J., Flynn, Connor, Springston, Stephen, Delgadillo, Rodrigo, Zhang, Jianhao, Aiken, Allison C., Koontz, Annette, & Muradyan, Paytsar. The Ascension Island boundary layer in the remote southeast Atlantic is often smoky. United States. doi:10.1002/2017GL076926.
Zuidema, Paquita, Sedlacek III, Arthur J., Flynn, Connor, Springston, Stephen, Delgadillo, Rodrigo, Zhang, Jianhao, Aiken, Allison C., Koontz, Annette, and Muradyan, Paytsar. Sat . "The Ascension Island boundary layer in the remote southeast Atlantic is often smoky". United States. doi:10.1002/2017GL076926. https://www.osti.gov/servlets/purl/1433942.
@article{osti_1433942,
title = {The Ascension Island boundary layer in the remote southeast Atlantic is often smoky},
author = {Zuidema, Paquita and Sedlacek III, Arthur J. and Flynn, Connor and Springston, Stephen and Delgadillo, Rodrigo and Zhang, Jianhao and Aiken, Allison C. and Koontz, Annette and Muradyan, Paytsar},
abstractNote = {Observations from June through 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. 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 indirectly indicate the presence of other light-absorbing aerosols (e.g., brown carbon), most pronounced in June. 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 of 2016, is investigated further. Also, backtrajectories indicate more direct boundary layer transport westward from the African continent is central to explaining the elevated surface aerosol loadings.},
doi = {10.1002/2017GL076926},
journal = {Geophysical Research Letters},
issn = {0094-8276},
number = 9,
volume = 45,
place = {United States},
year = {2018},
month = {3}
}

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Cited by: 6 works
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Figures / Tables:

Figure 1 Figure 1: 1 June - 31 October, 2016 time series of a) single-particle soot photometer (SP2)-derived refractory black carbon (rBC) mass concentrations. Monthly 10, 25, 50, 75, 90 percentiles are indicated, with a dotted line connecting monthly-mean values. b) Particle soot absorption photometer (PSAP) aerosol light absorption coefficients at threemore » wavelengths (blue: 464 nm, green: 529 nm, red: 648 nm) as an average of the ? and ? corrections (see SI for more detail). The inset indicates the relative frequency distribution of the blue-red absorption angstrom exponent, only calculated when the blue nephelometer-derived scattering > 10 Mm−1. c) Cloud condensation concentrations (CCN) at 0.1%, 0.2% and 0.4% supersaturations (data from 15 September to 1 November are missing). Inset indicates daily-averaged CCN versus rBC mass concentrations. d) Condensation particle concentrations (black; minimum particle diameter of 10 nm) and carbon monoxide (red). See Supplementary Information for more data description of all figures.« less

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Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.