Cloud condensation nuclei measurements in the marine boundary layer of the Eastern Mediterranean: CCN closure and droplet growth kinetics 1Environmental Chemical Processes Laboratory, Department of Chemistry, University of Crete, Voutes, 71003, Heraklion, Greece
2Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, GA, USA
3Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, 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
Received: 10 March 2009 – Published in Atmos. Chem. Phys. Discuss.: 27 April 2009 Abstract. Measurements of cloud condensation nuclei (CCN) concentrations (cm−3)
between 0.2 and 1.0% supersaturation, aerosol size distribution and
chemical composition were performed at a remote marine site in the eastern
Mediterranean, from September to October 2007 during the FAME07 campaign.
Most of the particles activate at ~0.6% supersaturation,
characteristic of the aged nature of the aerosol sampled. Application of
Köhler theory, using measurements of bulk composition, size
distribution, and assuming that organics are insoluble resulted in agreement
between predicted and measured CCN concentrations within 7±11% for
all supersaturations, with a tendency for CCN underprediction
(16±6%; r2=0.88) at the lowest supersaturations (0.21%). Including
the effects of the water-soluble organic fraction (which represent around
70% of the total organic content) reduces the average underprediction bias at the
low supersaturations, resulting in a total closure error of 0.6±6%.
Using threshold droplet growth analysis, the growth kinetics of ambient CCN
is consistent with NaCl calibration experiments; hence the presence of aged
organics does not suppress the rate of water uptake in this environment. The
knowledge of the soluble salt fraction is sufficient for the description of
the CCN activity in this area.
Revised: 21 August 2009 – Accepted: 31 August 2009 – Published: 24 September 2009
Citation: Bougiatioti, A., Fountoukis, C., Kalivitis, N., Pandis, S. N., Nenes, A., and Mihalopoulos, N.: Cloud condensation nuclei measurements in the marine boundary layer of the Eastern Mediterranean: CCN closure and droplet growth kinetics, Atmos. Chem. Phys., 9, 7053-7066, doi:10.5194/acp-9-7053-2009, 2009.