New Cloud Droplet Sampler: Optimization and Cloud Chemistry Experiments

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The Counterflow Virtual Impactor (CVI) is an inertial separation device for removing cloud droplets from their gaseous environment for subsequent chemical and physical analysis. In its present stage of development, the CVI is now being used by the P.I.'s group in both airborne and ground- based sampling of clouds. This new grant provides for the further development of the sampling probe and its application in cloud chemistry studies. There are four objectives. (1) to test design modifications to extend the range of measurable droplet sizes and to improve the sharpness of "cut-size" fractionation. (2) To better define the operating limitations of the device with respect to problems of droplet distortion, break-up, evaporation, and coalescence, using both experimental and theoretical approaches. (3) To apply the CVI in studies of dissolved labile species in cloud droplets, especially of sulfur dioxide. (4) To conduct field observations in clouds to explore chemical and physical questions that can be approached by measuring droplet properties as a function of particle size.