AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
The Importance of the Cloud Processing of Aerosols in Predicting in Aerosol Nucleation, Growth and CCN
JEFFREY PIERCE, Betty Croft, Dalhousie University
Abstract Number: 150 Working Group: Aerosols, Clouds, and Climate
Abstract Clouds are associated with large uncertainties in atmospheric models. Thus, any influence that clouds have on the evolution of aerosols may lead to uncertainties in aerosol predictions. In this presentation, we explore two influences of clouds on aerosols in the GEOS-Chem-TOMAS global aerosol microphysics model: (1) The aqueous oxidation of SO2 to form sulfate aerosol mass in activated aerosols as opposed to the gas-phase oxidation of SO2 to form H2SO4 vapors, and (2) the wet deposition of aerosols. The balance of aqueous oxidation versus gas-phase oxidation of SO2 plays a critical role in determining H2SO4 vapor concentrations and thus aerosol nucleation and growth rates. A 15% increase in the gas-phase oxidation rate of SO2 leads to a 7% increase in H2SO4 and a 2.5% change in CCN. Yet, there is large differences between models in the gas-phase/aqueous-phase oxidation split with gas-phase oxidation representing less than 1/4 to more than 1/3 depending on the model. We also tested the model sensitivity to a double of the aerosol wet removal rate. The wet deposition of aerosols directly removes CCN; however, it reduces the aerosol condensation sink allowing enhanced nucleation, growth and the formation of fresh CCN. Thus, changes CCN predictions are dampened to changes in aerosol wet-deposition rates.