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AGU: Journal of Geophysical Research, Atmospheres

 

Keywords

  • dust
  • black carbon
  • absorption
  • single scatter albedo

Index Terms

  • Atmospheric Composition and Structure: Aerosols and particles
  • Atmospheric Composition and Structure: Pressure, density, and temperature
  • Atmospheric Composition and Structure: Transmission and scattering of radiation
  • Atmospheric Composition and Structure: Troposphere—composition and chemistry
  • Atmospheric Composition and Structure: Troposphere—constituent transport and chemistry
Abstract
Cited By (67)
 

Abstract

Size distributions and mixtures of dust and black carbon aerosol in Asian outflow: Physiochemistry and optical properties

A. D. Clarke

School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, USA

Y. Shinozuka

School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, USA

V. N. Kapustin

School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, USA

S. Howell

School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, USA

B. Huebert

School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, USA

S. Doherty

Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA

T. Anderson

Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA

D. Covert

Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA

J. Anderson

Environmental Fluid Dynamics Program, Arizona State University, Tempe, Arizona, USA

X. Hua

Environmental Fluid Dynamics Program, Arizona State University, Tempe, Arizona, USA

K. G. Moore II

School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, USA

C. McNaughton

School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, Honolulu, Hawaii, USA

G. Carmichael

Department of Chemical and Biochemical Engineering, University of Iowa, Iowa City, Iowa, USA

R. Weber

School of the Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA

During Transport and Chemical Evolution over the Pacific (TRACE-P) and Asian Aerosol Characterization Experiment (ACE-Asia) we measured the dry size distribution of Asian aerosols, their state of mixing, and the optical properties of dust, black carbon (BC) and other aerosol constituents in combustion and/or dust plumes. Optical particle sizing in association with thermal heating extracted volatile components and resolved sizes for dust and refractory soot that usually dominated light absorption. BC was internally mixed with volatile aerosol in ∼85% of accumulation mode particles and constituted ∼5–15% of their mass. These optically effective sizes constrained the soot and dust size distributions and the imaginary part of the dust refractive index, k, to 0.0006 ± 0.0001. This implies a single-scatter albedo, ϖ (550 nm), for dust ranging from 0.99+ for D p <1 μm to ∼0.90 at D p = 10 μm and a size-integrated campaign average near 0.97 ± 0.01. The typical mass scattering efficiency for the dust was ∼0.3 m2 g−1, and the mass absorption efficiency (MAE) was 0.009 m2 g−1. Less dust south of 25°N and stronger biomass burning signatures resulted in lower values for ϖ of ∼0.82 in plumes aloft. Chemically inferred elemental carbon was moderately correlated with BC light absorption (R 2 = 0.40), while refractory soot volume between 0.1 and 0.5 μm was highly correlated (R 2 = 0.79) with absorption. However, both approaches yield an MAE for BC mixtures of ∼7 ± 2 m2 g−1 and higher than calculated MAE values for BC of 5 m2 g−1. The increase in the mass fraction of soot and BC in pollution aerosol in the presence of elevated dust appears to be due to uptake of the volatile components onto the coarse dust. This predictably lowered ϖ for the accumulation mode from 0.84 in typical pollution to ∼0.74 in high-dust events. A chemical transport model revealed good agreement between model and observed BC absorption for most of SE Asia and in biomass plumes but underestimated BC for combustion sources north of 25°N by a factor of ∼3.

Received 24 November 2003; accepted 18 March 2004; published 8 June 2004.

Citation: Clarke, A. D., et al. (2004), Size distributions and mixtures of dust and black carbon aerosol in Asian outflow: Physiochemistry and optical properties, J. Geophys. Res., 109, D15S09, doi:10.1029/2003JD004378.

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