Atmos. Chem. Phys. Discuss., 9, 5263-5287, 2009
www.atmos-chem-phys-discuss.net/9/5263/2009/
doi:10.5194/acpd-9-5263-2009
© Author(s) 2009. 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.
Effects of boundary layer particle formation on cloud droplet number and changes in cloud albedo from 1850 to 2000
J. Merikanto1, D. V. Spracklen1, K. J. Pringle2, and K. S. Carslaw1
1School of Earth and Environment, University of Leeds, Leeds, UK
2Max Planck Institute for Chemistry, Mainz, Germany

Abstract. We use a global aerosol microphysics model to estimate the effect of boundary layer particle formation on cloud droplet number concentration (CDNC) on global and regional scales. The calculations are carried out for years 1850 and 2000 using historical emissions inventories for primary particles and aerosol precursor gases. Predicted CDNC in 2000 are in good agreement with in-situ observations when particle formation is included. We find that particle formation increases global annual mean CDNC by approximately the same amount in both years (16.0% in 1850 and 13.5% in 2000). Thus, global mean changes in cloud albedo are similar with and without particle formation. However, there are substantial regional effects of up to 50% enhancement or suppression of the 1850–2000 albedo change. Over most modern-day polluted Northern Hemisphere regions particle formation suppresses the 1850–2000 increase in CDNC and cloud albedo. Over the Arctic the albedo change is suppressed by 23% in the annual mean and by 43% in summer when particle formation is taken into account. The albedo change of the persistent stratocumulus cloud deck west of Chile is enhanced by 49%.

Citation: Merikanto, J., Spracklen, D. V., Pringle, K. J., and Carslaw, K. S.: Effects of boundary layer particle formation on cloud droplet number and changes in cloud albedo from 1850 to 2000, Atmos. Chem. Phys. Discuss., 9, 5263-5287, doi:10.5194/acpd-9-5263-2009, 2009.
 
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