Atmos. Chem. Phys. Discuss., 12, 22687-22712, 2012
www.atmos-chem-phys-discuss.net/12/22687/2012/
doi:10.5194/acpd-12-22687-2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
A single parameter representation of hygroscopic growth and cloud condensation nucleus activity – Part 3: Including surfactant partitioning
M. D. Petters1 and S. M. Kreidenweis2
1Department of Marine Earth and Atmospheric Sciences, North Carolina State University, Raleigh, NC, USA
2Department of Atmospheric Science, Colorado State University, Fort Collins, CO, USA

Abstract. Atmospheric particles can serve as cloud condensation nuclei in the atmosphere. The presence of surface active compounds in the particle may affect the critical supersaturation that is required to activate a particle. Modelling surfactants in the context of Köhler theory, however, is difficult because surfactant enrichment at the surface implies that a stable radial concentration gradient must exist in the droplet. In this study, we introduce a hybrid model that accounts for partitioning between the bulk and surface phases in the context of single parameter representations of cloud condensation nucleus activity. The presented formulation incorporates the analytical approximations introduced by Raatikainen and Laaksonen to yield a set of equations that maintain the conceptual and mathematical simplicity of the single parameter framework. The resulting set of equations allows users of the single parameter model to account for surfactant partitioning by applying minor modifications to already existing code. We apply this extended model to discuss several uncertainties that hinder our ability to precisely pinpoint the role of surface tension in cloud droplet activation with current measurement and data analysis approaches.

Citation: Petters, M. D. and Kreidenweis, S. M.: A single parameter representation of hygroscopic growth and cloud condensation nucleus activity – Part 3: Including surfactant partitioning, Atmos. Chem. Phys. Discuss., 12, 22687-22712, doi:10.5194/acpd-12-22687-2012, 2012.
 
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