CCN in ACE-1

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9419263 Hudson This project is part of the Southern Hemisphere Marine Aerosol Characterization Experiment (ACE-1), which will be conducted in the remote Southern Pacific in 1995 using aircraft, ship-board, and ground-based measurements of a wide variety of chemical species, physical and meteorological parameters with the central goal of investigating the formation, evolution, and optical properties of atmospheric aerosol. In this component, cloud condensation nuclei will be measured onboard the NCAR C-130 aircraft, as well as at the ground in Cape Grim, Tasmania. These CCN measurements constitute one of the central objectives of the ACE-1 project, and provide a link between atmospheric chemistry and cloud research. The continuous airborne CCN measurements can be used to gauge the indirect aerosol effect, i.e. the suggested increase in cloud stability due to increased CCN concentrations. CCN spectra will be compared with physical and chemical aerosol characterizations to determine if CCN spectra can be predicted from chemical and physical properties of the aerosol. This is important for aerosol modeling, climate modeling, and determinations of the origin of atmospheric aerosol. Comparisons between CCN and cloud droplets provide the opportunity to separate macrophysical and microphysical cloud properties and to distinguish between the effects of cloud dynamics and the effects of the physics and chemistry of the aerosol. The ACE-1 data will constitute an extension of other CCN and cloud droplet data bases with the ultimate goal of understanding the role of aerosols in the global cloud systems.