Contribution of particle formation to global cloud condensation nuclei concentrations
We use a global aerosol microphysics model to predict the contribution of boundary layer (BL) particle formation to regional and global distributions of cloud condensation nuclei (CCN). Including an observationally derived particle formation scheme, where the formation rate of molecular clusters is proportional to gas-phase sulfuric acid to the power one, improves modeled particle size distribution and total particle number concentration at three continental sites in Europe. Particle formation increases springtime BL global mean CCN (0.2% supersaturation) concentrations by 3–20% and CCN (1%) by 5–50%. Uncertainties in particle formation and growth rates must be reduced before the accuracy of these predictions can be improved. These results demonstrate the potential importance of BL particle formation as a global source of CCN.