Atmos. Chem. Phys. Discuss., 10, 13945-13968, 2010
www.atmos-chem-phys-discuss.net/10/13945/2010/
doi:10.5194/acpd-10-13945-2010
© Author(s) 2010. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Constraints on first aerosol indirect effect from a combination of MODIS-CERES satellite data and global climate simulations
X. Ma1,2, K. von Salzen2, and J. Cole2
1School of Earth and Ocean Sciences University of Victoria, Victoria, British Columbia, Canada
2Canadian Centre for Climate Modelling and Analysis, Environment Canada, Victoria, British Columbia, Canada

Abstract. Retrievals of cloud top effective radius from MODIS (as derived by CERES) were combined with aerosol concentrations from the CCCma CanAM4 to examine relationships between aerosol and cloud that underlie the first aerosol indirect (cloud albedo) effect. Evidence of a strong negative relationship between sulphate, and organic aerosols, with cloud top effective radius was found for low clouds, indicating both aerosol types are contributing to the first indirect effect on a global scale. Furthermore, effects of aerosol on the cloud droplet effective radius are more pronounced for larger cloud liquid water paths. While CanAM4 broadly reproduces the observed relationship between sulphate aerosols and cloud droplets, it does not reproduce the dependency of cloud top droplet size on organic aerosol concentrations nor the dependency on cloud liquid water path. Simulations with a modified version of the model yield a more realistic dependency of cloud droplets on organic carbon. The robustness of the methods used in the study are investigated by repeating the analysis using aerosol simulated by the GOCART model and cloud top effective radii derived from the MODIS science team.

Citation: Ma, X., von Salzen, K., and Cole, J.: Constraints on first aerosol indirect effect from a combination of MODIS-CERES satellite data and global climate simulations, Atmos. Chem. Phys. Discuss., 10, 13945-13968, doi:10.5194/acpd-10-13945-2010, 2010.
 
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