The PI plans to extend an existing wintertime database of physical and chemical properties of cloud droplet populations at Storm Peak Laboratory Specifically, data will be collected far a two week period during December - January of 1991 - 1992 and 1992 - 1993, cloud droplet populations will be classified as maritime, continental, or "mixed" using concentration and diameter as criteria, back trajectories will be computed to determine the geographic location of SPL air parcels 48 hours prior to cloud sampling, and cloud water chemical analysis will be used to distinguish between droplet populations primarily formed on marine sulfate, crustal sulfate, or pollution sulfate. Additionally, complimentary aerosol measurements will be taken in clear conditions, and a 1 - D adiabatic cloud model will be used to determine a probable original CCN spectrum. Trends in total droplet concentration and mean diameter will also be determined using existing data with data collected as part of the proposed research.
