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Article
Aerosol Optical Hygroscopicity Measurements during the 2010 CARES Campaign
Atmospheric Chemistry and Physics
  • Dean B. Atkinson, Portland State University
  • James Gregory Radney, Portland State University
  • Janel Lum, Portland State University
  • Katheryn R. Kolesar, University of California - Davis
  • Daniel J. Cziczo, Massachusetts Institute of Technology
  • Mikhail Pekour, Pacific Northwest National Laboratory
  • Qi Zhang, University of California - Davis
  • Ari Setyan, Swiss Federal Laboratories for Materials Science and Technology
  • Alla Zelenyuk, Pacific Northwest National Laboratory
  • Christopher D. Cappa, University of California - Davis
Document Type
Article
Publication Date
4-1-2015
Subjects
  • Light -- Scattering -- Measurement,
  • Aerosols -- Optical properties,
  • Atmospheric aerosols
Abstract

Measurements of the effect of water uptake on particulate light extinction or scattering made at two locations during the 2010 CARES study around Sacramento, CA are reported. The observed influence of water uptake, characterized through the dimensionless optical hygroscopicity parameter γ, is compared with calculations constrained by observed particle size distributions and size-dependent particle composition. A closure assessment has been carried out that allowed for determination of the average hygroscopic growth factors (GF) at 85% relative humidity and the dimensionless hygroscopicity parameter κ for oxygenated organic aerosol (OA) and for supermicron particles, yielding κ = 0.1–0.15 and 0.9–1.0, respectively. The derived range of oxygenated OA κ values are in line with previous observations. The relatively large values for supermicron particles is consistent with substantial contributions of sea salt-containing particles in this size range. Analysis of time-dependent variations in the supermicron particle hygroscopicity suggest that atmospheric processing, specifically chloride displacement by nitrate and the accumulation of secondary organics on supermicron particles, can lead to substantial depression of the observed GF.

Description

© Author(s) 2014. This work is distributed under the Creative Commons Attribution 3.0 License.

This article is available online at: www.atmos-chem-phys.net/15/4045/2015/

DOI
10.5194/acp-15-4045-2015
Persistent Identifier
http://archives.pdx.edu/ds/psu/15122
Citation Information
Atkinson, D. B., Radney, J. G., Lum, J., Kolesar, K. R., Cziczo, D. J., Pekour, M. S., Zhang, Q., Setyan, A., Zelenyuk, A., and Cappa, C. D.: Aerosol optical hygroscopicity measurements during the 2010 CARES campaign, Atmos. Chem. Phys., 15, 4045-4061, doi:10.5194/acp-15-4045-2015, 2015.