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Copyright Copernicus GmbH 2011

Abstract

We propose that cloud condensation nuclei (CCN) concentrations are important for modulating ice formation of Arctic mixed-phase clouds, through modification of the droplet size distribution. Aircraft observations from the Aerosol, Radiation, and Cloud Processes affecting Arctic Climate (ARCPAC) study in northern Alaska in April 2008 allow for identification and characterization of both aerosol and trace gas pollutants, which are then compared with cloud microphysical properties. Consistent with previous studies, we find that the concentration of precipitating ice particles (>400 μm) is correlated with the concentration of large droplets (>30 μm). We are further able to link the observed microphysical conditions to aerosol pollution, originating mainly from long range transport of biomass burning emissions. The case studies demonstrate that polluted mixed-phase clouds have narrower droplet size distributions and contain 1-2 orders of magnitude fewer precipitating ice particles than clean clouds at the same temperature. This suggests an aerosol indirect effect leading to greater cloud lifetime, greater cloud emissivity, and reduced precipitation. This result is opposite to the glaciation indirect effect, whereby polluted clouds are expected to precipitate more readily due to an increase in the concentration of particles acting as ice nuclei.

Details

Title
Cloud condensation nuclei as a modulator of ice processes in Arctic mixed-phase clouds
Author
Lance, S.; Shupe, M. D.; Feingold, G.; Brock, C. A.; Cozic, J.; Holloway, J. S.; Moore, R. H.; Nenes, A.; Schwarz, J. P.; Spackman, J. R.; Froyd, K. D.; Murphy, D. M.; Brioude, J.; Cooper, O. R.; Stohl, A.; Burkhart, J. F.
First page
8003
Publication year
2011
Publication date
2011
Publisher
Copernicus GmbH
ISSN
16807316
e-ISSN
16807324
Source type
Scholarly Journal
Language of publication
English
ProQuest document ID
881184780
Copyright
Copyright Copernicus GmbH 2011