Effect of Primary Organic Sea Spray Emissions on Cloud Condensation Nuclei Concentrations

DANIEL WESTERVELT (1), Peter Adams (1), Richard Moore (2), Athanasios Nenes (2)

(1) Carnegie Mellon University (2) Georgia Institute of Technology

     Abstract Number: 823
     Last modified: July 30, 2010

Abstract
This work quantifies the primary marine organic aerosol global emission source as well as the effect of these emissionson cloud condensation nuclei (CCN) concentrations by implementing an organic sea spray source function into a series of global aerosol simulations. Using this source function, a global marine organic aerosol emission rate of 17.7 Tg C yr$^(-1) is estimated. Effect on CCN concentrations (0.2% supersaturation) is modeled using the Two-Moment Aerosol Sectional (TOMAS) microphysics algorithm coupled to the GISS II-prime general circulation model. Upon including primary marine organic aerosol in global simulations, changes in CCN concentrations are induced by changes in the amount of solute in particles as well as the ability of the organic matter to serve as surfactants. To explore surfactant effects, surface tension depression data from seawater samples taken near the Georgia coast were applied as a function of carbon concentrations. Results show that marine organic aerosol exert a localized influence on CCN(0.2%) concentrations, decreasing regional concentrations by no more than five percent and globally averaged concentrations by less than one percent. The decreases in CCN(0.2%) concentrations occur because of the partial replacement of soluble sea salt aerosol with less soluble oceanic organic matter. The low sensitivity of CCN(0.2%) to the marine organic emissions is likely due to the small compositional changes in the overall, internally mixed aerosol. Surfactant effects also contribute to the diminished sensitivity, lowering the globally-averaged relative change in CCN(0.2%) from 0.35% to 0.26%.