Inferring black carbon content and specific absorption from Aerosol Robotic Network (AERONET) aerosol retrievals

Gregory L. Schuster, Oleg Dubovik, Brent N. Holben, Eugene Edmund Clothiaux

Research output: Contribution to journalArticle

99 Citations (Scopus)

Abstract

Black carbon is ubiquitous in the atmosphere and is the main anthropogenic absorbing particulate. Absorption by black carbon is thought to be comparable to the cooling associated with sulfate aerosols, although present-day satellites are incapable of obtaining this measurement, and model estimates are highly uncertain. More measurements of black carbon concentration are necessary for improving and validating transport and general circulation models. The Aerosol Robotics Network (AERONET) of 180 worldwide radiometers offers an opportunity to obtain these measurements. We use the Maxwell Garnett effective medium approximation to infer the column-averaged black carbon concentration and specific absorption of AERONET retrievals at 46 locations. The yearly averaged black carbon column concentrations exhibit the expected regional dependence, with remote island locations having values about an order of magnitude lower than the continental biomass burning locations. The yearly averaged black carbon specific absorption cross section is consistent with other measured values, 9.9 m2 g-1 for 19,591 retrievals, but varies from 7.7 to 12.5 m2 g-1. We attribute this variability to the details of the size distributions and the fraction of black carbon contained in the aerosol mixture. We also used the Maxwell Garnett equations to parameterize the imaginary refractive index with respect to the black carbon volume fraction, enabling simple but accurate absorption estimates for aerosol mixtures when the black carbon fraction and size distribution is known. The black carbon concentrations that we derive from AERONET measurements correctly describe the radiance field and represent an alternative to absorption optical thickness in the link between models and AERONET measurements.

Original languageEnglish (US)
Pages (from-to)1-19
Number of pages19
JournalJournal of Geophysical Research D: Atmospheres
Volume110
Issue number10
DOIs
StatePublished - May 27 2005

Fingerprint

Soot
black carbon
aerosols
Aerosols
robotics
retrieval
Robotics
aerosol
carbon
AERONET
soot
biomass burning
General Circulation Models
radiometers
refractive index
Maxwell equations
Radiometers
estimates
radiance
Maxwell equation

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

Cite this

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abstract = "Black carbon is ubiquitous in the atmosphere and is the main anthropogenic absorbing particulate. Absorption by black carbon is thought to be comparable to the cooling associated with sulfate aerosols, although present-day satellites are incapable of obtaining this measurement, and model estimates are highly uncertain. More measurements of black carbon concentration are necessary for improving and validating transport and general circulation models. The Aerosol Robotics Network (AERONET) of 180 worldwide radiometers offers an opportunity to obtain these measurements. We use the Maxwell Garnett effective medium approximation to infer the column-averaged black carbon concentration and specific absorption of AERONET retrievals at 46 locations. The yearly averaged black carbon column concentrations exhibit the expected regional dependence, with remote island locations having values about an order of magnitude lower than the continental biomass burning locations. The yearly averaged black carbon specific absorption cross section is consistent with other measured values, 9.9 m2 g-1 for 19,591 retrievals, but varies from 7.7 to 12.5 m2 g-1. We attribute this variability to the details of the size distributions and the fraction of black carbon contained in the aerosol mixture. We also used the Maxwell Garnett equations to parameterize the imaginary refractive index with respect to the black carbon volume fraction, enabling simple but accurate absorption estimates for aerosol mixtures when the black carbon fraction and size distribution is known. The black carbon concentrations that we derive from AERONET measurements correctly describe the radiance field and represent an alternative to absorption optical thickness in the link between models and AERONET measurements.",
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Inferring black carbon content and specific absorption from Aerosol Robotic Network (AERONET) aerosol retrievals. / Schuster, Gregory L.; Dubovik, Oleg; Holben, Brent N.; Clothiaux, Eugene Edmund.

In: Journal of Geophysical Research D: Atmospheres, Vol. 110, No. 10, 27.05.2005, p. 1-19.

Research output: Contribution to journalArticle

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