AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Global Modeling of SOA: The Use of Different Mechanisms for Aqueous Phase Formation
GUANGXING LIN, Joyce Penner, Sanford Sillman, Akinori Ito, University of Michigan
Abstract Number: 555 Working Group: Carbonaceous Aerosols in the Atmosphere
Abstract There is growing interest in the formation of secondary organic aerosol (SOA) through condensed aqueous phase reactions. In this study, we use a global model (IMPACT) to investigate the potential formation of SOA in the aqueous phase. We compare results from several multiphase process schemes with detailed aqueous phase reactions to schemes that use a first order gas-to-particle formation rate based on uptake coefficients. The predicted net global SOA production rate in cloud water ranges from 13.1 Tg/yr to 46.8 Tg/yr while that in aerosol water ranges from -0.4 Tg/yr to 12.6 Tg/yr. The predicted global burden of SOA formed in the aqueous phase ranges from 0.09 Tg to 0.51 Tg. A sensitivity test to investigate two representations of cloud water content from two global models shows that increasing cloud water by an average factor of 2.7 can increase the net SOA production rate in cloud by a factor of 4 at low altitudes (below approximately 900 hPa). We also investigated the importance of including dissolved iron chemistry in cloud water aqueous reactions. Adding these reactions increases the formation rate of aqueous phase OH by a factor of 2.6 and decreases the amount of global aqueous SOA formed by 31%. None of the mechanisms discussed here is able to provide a best fit for all observations. Rather, the use of an uptake coefficient method for aerosol water and a multi-phase scheme for cloud water provides the best fit in the Northern Hemisphere and the use of multiphase process scheme for aerosol and cloud water provides the best fit in the tropics. The model with iron chemistry under predicts oxalate measurements in all regions.