Aerosol-cloud Interactions of Secondary Organic Aerosols Formed from the Oxidation of Linear, Branched, and Cyclic Alkanes and Alkenes

Markus Petters North Carolina State University
Annelise Faulhaber University of Riverside
Anthony Prenni Colorado State University
Paul DeMott Colorado State University
Roger Atkinson University of California
Janet Arey University of California
Sonia Kreidenweis Colorado State University
Paul Ziemann University of California
Christian Carrico Colorado State University
Ryan Sullivan Carnegie Mellon University

Category: Aerosol-Cloud-Radiation Interactions

Working Group: Cloud-Aerosol-Precipitation Interaction

Secondary organic aerosols (SOA) formed from anthropogenic and biogenic precursors comprise a significant fraction of the atmospheric aerosol burden and play an important role in the Earth’s radiation budget. To obtain a prognostic understanding of the impacts of SOA on clouds and climate, we must relate the chemical composition of the compounds that are found in the aerosol to their cloud forming potential. Unfortunately the chemical mechanisms that govern SOA formation result in an intractable number of species. Therefore, models operating at any scale need to introduce optimally aggregated aerosol properties to minimize the number of classes that must be tracked. Towards this goal, we conducted measurements of the cloud condensation nuclei (CCN) and ice nuclei activity of secondary organic aerosol that was formed from the oxidation of linear, branched, and cyclic alkanes and alkenes. Aerosol forming reactions were carried out in a FEP environmental chamber, including oxidation of the precursors with O3, NO3, and OH in the presence and absence of NOx. Ice nucleation experiments were performed only for the O3 reactions, and ice nuclei were not observed in detectable quantities for this subset of systems. When expressed as hygroscopicity parameter (kappa), CCN activity ranged from kappa = 0.15 to kappa ~ 0, spanning the range from moderately CCN active to CCN inactive at atmospherically relevant sizes and supersaturations, respectively. The observed relationships between the organic aerosols’ physical and chemical properties and its apparent cloud condensation nucleus activity allows us to constrain the organic aerosol behavior by grouping along the conceptual axes of precursor molecular size and types of functional groups associated with the carbon chain. The data suggest certain groupings that may provide a prognostic link between a source process (e.g. terpene emissions) and the effective behavior of the formed aerosol relevant to aerosol-cloud-climate interactions.

This poster will be displayed at ASR Science Team Meeting.