Articles | Volume 11, issue 16
Atmos. Chem. Phys., 11, 8791–8808, 2011

Special issue: European Integrated Project on Aerosol-Cloud-Climate and Air...

Atmos. Chem. Phys., 11, 8791–8808, 2011

Research article 30 Aug 2011

Research article | 30 Aug 2011

Size-resolved CCN distributions and activation kinetics of aged continental and marine aerosol

A. Bougiatioti1, A. Nenes2,3,4, C. Fountoukis3,4, N. Kalivitis1, S. N. Pandis4,5, and N. Mihalopoulos1,4 A. Bougiatioti et al.
  • 1Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, Voutes, 71003, Heraklion, Greece
  • 2Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, 30332, USA
  • 3Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
  • 4Institute of Chemical Engineering and High Temperature Chemical Processes (ICE-HT), Foundation for Research and Technology Hellas (FORTH), Patras, 26504, Greece
  • 5Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, PA, 15213, USA

Abstract. We present size-segregated measurements of cloud condensation nucleus (CCN) activity of aged aerosol sampled at Finokalia, Crete, during the Finokalia Aerosol Measurement Experiment of summer 2007 (FAME07). From analysis of the data, hygroscopicity and activation kinetics distributions are derived. The CCN are found to be highly hygroscopic, (expressed by a size- and time- averaged hygroscopicity parameter κ ∼ 0.22), with the majority of particles activating at ~0.5–0.6 % supersaturation. Air masses originating from Central-Eastern Europe tend to be associated with higher CCN concentrations and slightly lower hygroscopicity (κ ∼ 0.18) than for other airmass types. The particles were always well mixed, as reflected by the high activation ratios and narrow hygroscopicity distribution widths. Smaller particles (~40 nm) were found to be more hygroscopic (~0.1κ units higher) than the larger ones (~100 nm). The particles with diameters less than 80 nm exhibited a diurnal hygroscopicity cycle (with κ peaking at ~14 h local time), consistent with photochemical aging and volatilization of less hygroscopic material from the aerosol. Use of bulk chemical composition and the aerosol number distribution results in excellent CCN closure when applying Köhler theory in its simplest form. Using asymptotic and threshold droplet growth analysis, the "aged" organics present in the aerosol were found not to suppress or delay the water uptake kinetics of particles in this environment.

Final-revised paper