AAAR 34th Annual Conference
October 12 - October 16, 2015
Hyatt Regency
Minneapolis, Minnesota, USA
Abstract View
Critical Time for CCN Activation of Biogenic Precursors
ASHLEY VIZENOR, Akua Asa-Awuku, University of California, Riverside
Abstract Number: 133 Working Group: Aerosols, Clouds, and Climate
Abstract Particles that can uptake water and form cloud droplets are referred to as cloud condensation nuclei (CCN). The hygroscopicity, or ability of a particle to activate is traditionally quantified by a single parameter, kappa. Here we examined the photooxidation of two biogenic compounds, isoprene and longifolene using the UCR CE-CERT Environmental Chamber. A TSI SMPS ran in parallel with a Droplet Measurement Technologies Cloud Condensation Nuclei Counter (CCNC) was used to observe the hygroscopicity of resulting secondary organic aerosol (SOA). Traditional CCN analysis is performed by dividing the number of particles activated by the total number of particles (condensation nuclei, CN). The point at which the ratio equals 0.5 is used to identify the critical supersaturation at which 50% of the particles activate for a given diameter. Alternatively, the critical diameter at which 50% of particles for a given supersaturation can be identified. This critical supersaturation and the corresponding dry diameter are then used to calculate kappa. However, this calculation assumes that the hygroscopicity of particles stays constant for a given precursor gas. The CCN to CN ratio at given diameters and supersaturations was calculated and plotted against photooxidation time to observe if this assumption holds true.