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Cloud Condensation Nuclei Prediction Error from Application of Kohler Theory: Importance for the Aerosol Indirect EffectIn situ observations of aerosol and cloud condensation nuclei (CCN) and the GISS GCM Model II' with an online aerosol simulation and explicit aerosol-cloud interactions are used to quantify the uncertainty in radiative forcing and autoconversion rate from application of Kohler theory. Simulations suggest that application of Koehler theory introduces a 10-20% uncertainty in global average indirect forcing and 2-11% uncertainty in autoconversion. Regionally, the uncertainty in indirect forcing ranges between 10-20%, and 5-50% for autoconversion. These results are insensitive to the range of updraft velocity and water vapor uptake coefficient considered. This study suggests that Koehler theory (as implemented in climate models) is not a significant source of uncertainty for aerosol indirect forcing but can be substantial for assessments of aerosol effects on the hydrological cycle in climatically sensitive regions of the globe. This implies that improvements in the representation of GCM subgrid processes and aerosol size distribution will mostly benefit indirect forcing assessments. Predictions of autoconversion, by nature, will be subject to considerable uncertainty; its reduction may require explicit representation of size-resolved aerosol composition and mixing state.
Document ID
20080034467
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Sotiropoulou, Rafaella-Eleni P.
(Georgia Inst. of Tech. Atlanta, GA, United States)
Nenes, Athanasios
(Georgia Inst. of Tech. Atlanta, GA, United States)
Adams, Peter J.
(Carnegie-Mellon Univ. Pittsburgh, PA, United States)
Seinfeld, John H.
(California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
August 24, 2013
Publication Date
June 1, 2007
Publication Information
Publication: Journal of Geophysical Research
Publisher: American Geophysical Union
Volume: 112
Subject Category
Meteorology And Climatology
Funding Number(s)
CONTRACT_GRANT: NNG04GD53G
Distribution Limits
Public
Copyright
Other

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