AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
The Ice Nucleating Potential of Amorphous Secondary Organic Aerosol to Form Cold Clouds
BINGBING WANG, Andrew Lambe, Paola Massoli, Timothy Onasch, Paul Davidovits, Douglas Worsnop, Daniel Knopf, Stony Brook University
Abstract Number: 616 Working Group: Aerosols, Clouds, and Climate
Abstract Secondary organic aerosol (SOA) generated from the oxidation of organic gases are ubiquitous in the atmosphere, but their interaction with water vapor and their ice cloud formation potential at low temperatures remains highly uncertain. We report on measurements of water uptake and ice nucleation of laboratory-generated SOA that exhibit similar behavior to ambient organic particles. Water uptake above 230 K is governed by the oxidation level of the SOA, followed by moisture-induced phase transitions and immersion freezing. For temperatures from 200 to 230 K, the SOA nucleate ice from supersaturated water vapor independent of oxidation level. We show that particle phase and viscosity govern the particles' response to temperature and relative humidity and provide a straightforward interpretation for the observations of both laboratory and ambient organic particles. Since SOA undergo glass transitions, these observations suggest that atmospheric SOA are potentially important for ice cloud formation and climate.