7A.6 Susceptibility of cloud characteristics to aerosols over Europe: Study with WRF/Chem

Tuccella, Paolo, Gabriele Curci, and Guido Visconti, University of L'Aquila, Italy

The new parameterization for secondary organic aerosol yield based on the volatile basis set implemented in WRF/Chem recently, has been coupled with the microphysics of clouds. The effects of this new mechanism is evaluated through the comparison of high resolution simulations on a cloud resolving domain against the groud-based and aircraft measurements of aerosol chemical composition and particles, and cloud microphysics, issued in the frame of European Integrated project on the Aerosol Cloud Climate and Air Quality Interaction (EUCAARI).

The central topic of this study is to address the question: how well does WRF/Chem reproduce the amplitude of aerosol indirect effects? The aerosol cloud interaction (ACI) effect has been calculated as ACI=-(∂lnr_e)/∂lnN, where re is the cloud droplet effective radius and N aerosol particle number of each mode of log-normal distribution. Observations attribute the indirect effect to total aerosol particle number with a value of -0.22, very close to theoretical value of -0.23. Instead, WRF/Chem reproduces the observed amplitude of ACI, but attributes it to the particles of accumulation mode, while the observations indicate a strong ACI due to total particle number. The reasons of this results are under investigation.