Role of molecular size in cloud droplet activation

M. D. Petters, S. M. Kreidenweis, A. J. Prenni, R. C. Sullivan, C. M. Carrico, K. A. Koehler, P. J. Ziemann

Research output: Contribution to journalArticlepeer-review

47 Scopus citations


We examine the observed relationships between molar volume (the ratio of molar mass and density) and cloud condensation nuclei (CCN) activity for sufficiently soluble organic compounds found in atmospheric particulate matter. Our data compilation includes new CCN data for certain carbohydrates and oligoethylene glycols, as well as published data for organic compounds. We compare predictions of CCN activity using water activities based on Raoult's law and Flory-Huggins theory to observations. The Flory-Huggins water activity expression, with an assumed surface tension of pure water, generally predicts CCN activity within a factor of two over the full range of molar volumes considered. CCN activity is only weakly dependent on molar volume for values exceeding 600 cm3 mol-1, and the diminishing sensitivity to molar volume, combined with the significant scatter in the data, limits the accuracy with which molar volume can be inferred from CCN measurements.

Original languageEnglish (US)
Article numberL22801
JournalGeophysical Research Letters
Issue number22
StatePublished - Nov 2009
Externally publishedYes

ASJC Scopus subject areas

  • Geophysics
  • General Earth and Planetary Sciences


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