Articles | Volume 15, issue 13
Atmos. Chem. Phys., 15, 7585–7604, 2015
Atmos. Chem. Phys., 15, 7585–7604, 2015

Research article 13 Jul 2015

Research article | 13 Jul 2015

The relationship between cloud condensation nuclei (CCN) concentration and light extinction of dried particles: indications of underlying aerosol processes and implications for satellite-based CCN estimates

Y. Shinozuka1,2, A. D. Clarke3, A. Nenes4,5, A. Jefferson6,7, R. Wood8, C. S. McNaughton3,9, J. Ström10, P. Tunved10, J. Redemann11, K. L. Thornhill12, R. H. Moore13, T. L. Lathem4,14, J. J. Lin4, and Y. J. Yoon15 Y. Shinozuka et al.
  • 1NASA Ames Research Center Cooperative for Research in Earth Science and Technology, Moffett Field, California, USA
  • 2Bay Area Environmental Research Institute, Petaluma, California, USA
  • 3School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, Hawaii, USA
  • 4School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia, USA
  • 5School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia, USA
  • 6Cooperative Institute for Research in Environmental Science (CIRES), University of Colorado, Boulder, Colorado, USA
  • 7NOAA Earth System Research Laboratory, Boulder, Colorado, USA
  • 8Department of Atmospheric Sciences, University of Washington, Seattle, Washington, USA
  • 9Golder Associates Ltd., Saskatoon, Saskatchewan, Canada
  • 10Department of Applied Environmental Science, Stockholm University, Stockholm, Sweden
  • 11NASA Ames Research Center, Moffett Field, California, USA
  • 12Science Systems and Applications Inc., Hampton, Virginia, USA
  • 13NASA Langley Research Center, Hampton, Virginia, USA
  • 14Phillips 66 Research Center, Bartlesville, Oklahoma, USA
  • 15Korea Polar Research Institute, Yeonsu-Gu, Incheon, Korea

Abstract. We examine the relationship between the number concentration of boundary-layer cloud condensation nuclei (CCN) and light extinction to investigate underlying aerosol processes and satellite-based CCN estimates. For a variety of airborne and ground-based observations not dominated by dust, regression identifies the CCN (cm−3) at 0.4 ± 0.1% supersaturation with 100.3α +1.3σ0.75 where σ (Mm−1) is the 500 nm extinction coefficient by dried particles and α is the Angstrom exponent. The deviation of 1 km horizontal average data from this approximation is typically within a factor of 2.0. ∂logCCN / ∂logσ is less than unity because, among other explanations, growth processes generally make aerosols scatter more light without increasing their number. This, barring special meteorology–aerosol connections, associates a doubling of aerosol optical depth with less than a doubling of CCN, contrary to previous studies based on heavily averaged measurements or a satellite algorithm.

Final-revised paper