Cloud condensation nuclei spectra derived from size distributions and hygroscopic properties of the aerosol in coastal south-west Portugal during ACE-2

In this work we propose and test a method to calculate cloud condensation nuclei (CCN) spectra based on aerosol number size distribution., and hygroscopic growth factors, Sensitivity Studies Show that this method can be used in a wide variety of conditions except Mien the aerosol consist mainly of organic Compounds, One crucial step in the calculations. estimating soluble tons in an aerosol particle based on hygroscopic growth factors. is tested in an internal hygroscopic consistency study. The results show that during the second Aerosol Characterization Experiment (ACE-2) the number concentration of inorganic ions analyzed in impactor samples Could be reproduced from measured growth factors within the measurement uncertainties it the measurement site in Sagres. Portugal. CCN spectra were calculated based on data from the ACE-2 field experiment at the Sagres site. The calculations overestimate measured CCN spectra on average by approximately 30%, which is comparable to the uncertainties in measurement, and calculations at supersaturations below 0.5%. The calculated CCN spectra were averaged over time periods with Sagres received clean air masses and air masses influenced by aged and recent pollution, Pollution outbreaks enhance the CCN concentrations at supersaturations near 0.2% by a factor of 3 (aged Pollution) to 5 (recent pollution) compared to the clean marine background concentrations. In polluted air masses, the shape of the CCN spectra changes. The clean spectra can he approximated h a poker function, whereas the polluted spectra are better approximated by an error function.