2nd Symposium on Aerosol-Cloud-Climate Interactions
12th Conference on Atmospheric Chemistry


Size-resolved Scanning Flow CCN Analysis (SFCA): A method for fast measurements of CCN spectra

Richard H. Moore, Georgia Institute of Technology, Atlanta, GA; and A. Nenes

The Continuous-Flow Streamwise Thermal-Gradient Cloud Condensation Nuclei Counter1 is a commercially-available instrument that is widely used for laboratory and field measurements of cloud condensation nuclei (CCN). Typically, the instrument is operated at a constant flow rate, and supersaturation is adjusted by changing the column streamwise temperature difference, which is slow (20-40 seconds, and sometimes more) and may introduce particle volatilization biases2. We present a new mode of operation, termed "Scanning Flow CCN Analysis" (SFCA), in which the flow rate in the growth chamber is changed over time, while maintaining a constant temperature gradient. This causes supersaturation to continuously change, allowing the rapid and continuous measurement of supersaturation spectra over timescales relevant for airborne measurements (10-60 seconds and potentially even less) without being affected from shifts in activation kinetics and aerosol composition. We present results of size-resolved CCN spectra obtained using SFCA, coupled with an electrostatic classifier to demonstrate the application of the technique to ambient measurements of urban aerosol.

1Roberts, G. and A. Nenes. Aerosol Sci. Technol., 39, 2005

2Asa-Awuku, A., et al., Atmos. Chem. Phys., 9, 2009.

Joint Poster Session , Aerosol, Cloud, and Climate
Wednesday, 20 January 2010, 2:30 PM-4:00 PM, Exhibit Hall B2

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