Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

IF value: 5.414
IF5.414
IF 5-year value: 5.958
IF 5-year
5.958
CiteScore value: 9.7
CiteScore
9.7
SNIP value: 1.517
SNIP1.517
IPP value: 5.61
IPP5.61
SJR value: 2.601
SJR2.601
Scimago H <br class='widget-line-break'>index value: 191
Scimago H
index
191
h5-index value: 89
h5-index89
Volume 10, issue 1
Atmos. Chem. Phys., 10, 299–312, 2010
https://doi.org/10.5194/acp-10-299-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 10, 299–312, 2010
https://doi.org/10.5194/acp-10-299-2010
© Author(s) 2010. This work is distributed under
the Creative Commons Attribution 3.0 License.

  15 Jan 2010

15 Jan 2010

Slower CCN growth kinetics of anthropogenic aerosol compared to biogenic aerosol observed at a rural site

N. C. Shantz1,*, R. Y.-W. Chang1, J. G. Slowik1, A. Vlasenko1,*, J. P. D. Abbatt1, and W. R. Leaitch2 N. C. Shantz et al.
  • 1Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
  • 2Science and Technology Branch, Environment Canada, Toronto, Ontario, Canada
  • *now at: Science and Technology Branch, Environment Canada, Toronto, Ontario, Canada

Abstract. Growth rates of water droplets were measured with a static diffusion cloud condensation chamber in May–June 2007 at a rural field site in Southern Ontario, Canada, 70 km north of Toronto. The observations include periods when the winds were from the south and the site was impacted by anthropogenic air from the U.S. and Southern Ontario as well as during a 5-day period of northerly wind flow when the aerosol was dominated by biogenic sources. The growth of droplets on anthropogenic size-selected particles centred at 0.1 μm diameter and composed of approximately 40% organic and 60% ammonium sulphate (AS) by mass, was delayed by on the order of 1 s compared to a pure AS aerosol. Simulations of the growth rate on monodisperse particles indicate that a lowering of the water mass accommodation coefficient from αc=1 to an average of αc=0.04 is needed (assuming an insoluble organic with hygroscopicity parameter, κorg, of zero). Simulations of the initial growth rate on polydisperse anthropogenic particles agree best with observations for αc=0.07. In contrast, the growth rate of droplets on size-selected aerosol of biogenic character, consisting of >80% organic, was similar to that of pure AS. Simulations of the predominantly biogenic polydisperse aerosol show agreement between the observations and simulations when κorg=0.2 (with upper and lower limits of 0.5 and 0.07, respectively) and αc=1. Inhibition of water uptake by the anthropogenic organic applied to an adiabatic cloud parcel model in the form of a constant low αc increases the number of droplets in a cloud compared to pure AS. If the αc is assumed to increase with increasing liquid water on the droplets, then the number of droplets decreases which could diminish the indirect climate forcing effect. The slightly lower κorg in the biogenic case decreases the number of droplets in a cloud compared to pure AS.

Publications Copernicus
Download
Citation
Altmetrics
Final-revised paper
Preprint