Observations of single scattering Albedo made during the 2007 cumulus humilis aerosol processing study: size or composition?

The Cumulus Humilis Aerosol Processing Study (CHAPS) was carried out in the vicinity of Oklahoma City, OK between June 1 and June 30, 2007. The airborne measurements of this project were designed to examine the influence of anthropogenic aerosols from a mid-size urban area on the microphysics of cumuliform clouds, and the effects of these clouds on urban aerosols that pass through fields of fair weather cumulus (FWC). In this presentation, we will describe observations from CHAPS that are available for use by the general atmospheric science community and then discuss key findings related to the single scattering albedo (SSA). Systematic changes in SSA were observed during conditions characterized as a) clean and non-cloudy, b) clean and cloudy, c) dirty and non-cloudy, and c) dirty and cloudy. These observations of SSA will then be related to corresponding changes in 1) the total observed particle loading for both activated and interstitial particles, 2) changes in the Angstrom Exponent and 3) particle composition. Our preliminary analysis suggests a strong inverse relation between organic matter found above cloud top and SSA which does not appear to be related to the presence of black carbon.