Role of molecular size in cloud droplet activation
Article first published online: 17 NOV 2009
Copyright 2009 by the American Geophysical Union.
Geophysical Research Letters
Volume 36, Issue 22, November 2009
How to Cite
2009), Role of molecular size in cloud droplet activation, Geophys. Res. Lett., 36, L22801, doi:10.1029/2009GL040131., , , , , , and (
- Issue published online: 17 NOV 2009
- Article first published online: 17 NOV 2009
- Manuscript Accepted: 5 OCT 2009
- Manuscript Revised: 27 SEP 2009
- Manuscript Received: 22 JUL 2009
- organic aerosol;
- cloud condensation nuclei;
- high molecular weight compounds
 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.