ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-10-6855-2010 Empirical estimates of CCN from aerosol optical properties at four remote sites Jefferson A. 1 2 Cooperative Institute for Research in Environmental Science (CIRES), University of Colorado, Boulder, CO, USA NOAA Earth System Research Laboratory, Boulder, CO, USA 23 07 2010 10 14 6855 6861 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/10/6855/2010/acp-10-6855-2010.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/10/6855/2010/acp-10-6855-2010.pdf

This study presents an empirical method to estimate the CCN concentration as a function of percent supersaturation. The aerosol optical properties, backscatter fraction and single scatter albedo, function as proxies for the aerosol size and composition in a power law relationship to CCN. This method is tested at four sites with aged aerosol: SGP (Oklahoma, USA), FKB (Black Forest, Germany), HFE (Hefei, China) and GRW (Graciosa, Azores). Each site represents a different aerosol type and thus demonstrates the method robustness and limitations. Good agreement was found between the calculated and measured CCN with slopes between 0.81 and 1.03 and correlation coefficients (<i>r</i><sup>2</sup> values) between 0.59 and 0.67. The fit quality declined at low CCN concentrations.

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