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Title: An interfacial mechanism for cloud droplet formation on organic aerosols

Accurate predictions of aerosol/cloud interactions require simple, physically accurate parameterizations of the cloud condensation nuclei (CCN) activity of aerosols. Current models assume that organic aerosol species contribute to CCN activity by lowering water activity. We measured droplet diameters at the point of CCN activation for particles composed of dicarboxylic acids or secondary organic aerosol and ammonium sulfate. Droplet activation diameters were 40 to 60% larger than predicted if the organic was assumed to be dissolved within the bulk droplet, suggesting that a new mechanism is needed to explain cloud droplet formation. A compressed film model explains how surface tension depression by interfacial organic molecules can alter the relationship between water vapor supersaturation and droplet size (i.e., the Köhler curve), leading to the larger diameters observed at activation.
Authors:
 [1] ;  [1] ;  [1]
  1. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Science
Additional Journal Information:
Journal Volume: 351; Journal Issue: 6280; Journal ID: ISSN 0036-8075
Publisher:
AAAS
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1454460

Ruehl, C. R., Davies, J. F., and Wilson, K. R.. An interfacial mechanism for cloud droplet formation on organic aerosols. United States: N. p., Web. doi:10.1126/science.aad4889.
Ruehl, C. R., Davies, J. F., & Wilson, K. R.. An interfacial mechanism for cloud droplet formation on organic aerosols. United States. doi:10.1126/science.aad4889.
Ruehl, C. R., Davies, J. F., and Wilson, K. R.. 2016. "An interfacial mechanism for cloud droplet formation on organic aerosols". United States. doi:10.1126/science.aad4889. https://www.osti.gov/servlets/purl/1454460.
@article{osti_1454460,
title = {An interfacial mechanism for cloud droplet formation on organic aerosols},
author = {Ruehl, C. R. and Davies, J. F. and Wilson, K. R.},
abstractNote = {Accurate predictions of aerosol/cloud interactions require simple, physically accurate parameterizations of the cloud condensation nuclei (CCN) activity of aerosols. Current models assume that organic aerosol species contribute to CCN activity by lowering water activity. We measured droplet diameters at the point of CCN activation for particles composed of dicarboxylic acids or secondary organic aerosol and ammonium sulfate. Droplet activation diameters were 40 to 60% larger than predicted if the organic was assumed to be dissolved within the bulk droplet, suggesting that a new mechanism is needed to explain cloud droplet formation. A compressed film model explains how surface tension depression by interfacial organic molecules can alter the relationship between water vapor supersaturation and droplet size (i.e., the Köhler curve), leading to the larger diameters observed at activation.},
doi = {10.1126/science.aad4889},
journal = {Science},
number = 6280,
volume = 351,
place = {United States},
year = {2016},
month = {3}
}