Recent Findings from In-Cloud Physicochemical Measurements in California Coastal Zone Stratocumulus Clouds

This study reports on chemical and physical properties of cloud water, droplet residual particles, and aerosol particles near clouds during two recent aircraft field campaigns off the California coast: the 2011 Eastern Pacific Emitted Aerosol Cloud Experiment (E-PEACE) and the 2013 Nucleation in California Experiment (NICE). These studies afforded the opportunity to examine the relationships between cloud water, droplet residual particles, and out-of-cloud particles as a function of meteorology and emissions from the ocean, ships, continental anthropogenic emissions, and biomass burning. Cloud water measurements were conducted with a slotted-rod collector, while droplet residual particle properties were measured downstream of a counterflow virtual impactor (CVI). The pH and concentrations of both water-soluble ions and elements were quantified in cloud water. Properties examined behind the CVI included particle size distributions, non-refractory and water-soluble composition, and hygroscopic properties. The results to be presented explore both cloud effects on aerosol and aerosol effects on cloud, including the following: (i) sources and sinks of secondarily produced aerosol species, (ii) the relative importance of primary particle emissions in altering cloud drop properties, and (iii) the nature of what particles preferentially activate into drops in the study region.