Articles | Volume 12, issue 23
Atmos. Chem. Phys., 12, 11573–11587, 2012
https://doi.org/10.5194/acp-12-11573-2012

Special issue: The CERN CLOUD experiment (ACP/AMT inter-journal SI)

Atmos. Chem. Phys., 12, 11573–11587, 2012
https://doi.org/10.5194/acp-12-11573-2012

Research article 04 Dec 2012

Research article | 04 Dec 2012

No statistically significant effect of a short-term decrease in the nucleation rate on atmospheric aerosols

E. M. Dunne1,2, L. A. Lee1, C. L. Reddington1, and K. S. Carslaw1 E. M. Dunne et al.
  • 1School of Earth and Environment, University of Leeds, Leeds, LS2 9JT, UK
  • 2Finnish Meteorological Institute, Kuopio Unit, Kuopio, Finland

Abstract. Observed correlations between short-term decreases in cosmic ray ionisation and cloud and aerosol properties have been attributed to short-term decreases in the ion-induced nucleation rate. We use a global aerosol microphysics model to determine whether a 10 day reduction of 15% in the nucleation rate could generate a statistically significant response in aerosol concentrations and optical properties. As an upper limit to the possible effect of changes in ion-induced nucleation rate, we perturb the total nucleation rate, which has been shown to generate particle concentrations and nucleation events in reasonable agreement with global observations. When measured against a known aerosol control state, the model predicts a 0.15% decrease in global mean cloud condensation nucleus concentration at the surface. However, taking into account the variability in aerosol, no statistically significant response can be detected in concentrations of particles with diameters larger than 10 nm, in cloud condensation nuclei with diameters larger than 70 nm, or in the Ångström exponent. The results suggest that the observed correlation between short-term decreases in cosmic ray ionisation and cloud and aerosol properties cannot be explained by associated changes in the large-scale nucleation rate.

Download
Altmetrics
Final-revised paper
Preprint