 |
| Titel |
Effect of primary organic sea spray emissions on cloud condensation nuclei concentrations |
| VerfasserIn |
D. M. Westervelt, R. H. Moore, A. Nenes, P. J. Adams |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 1 ; Nr. 12, no. 1 (2012-01-02), S.89-101 |
| Datensatznummer |
250010422
|
| Publikation (Nr.) |
 copernicus.org/acp-12-89-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| This work estimates the primary marine organic aerosol global emission
source and its impact on cloud condensation nuclei (CCN) concentrations by
implementing an organic sea spray source function into a series of global
aerosol simulations. The source function assumes that a fraction of the sea
spray emissions, depending on the local chlorophyll concentration, is
organic matter in place of sea salt. Effect on CCN concentrations (at
0.2% supersaturation) is modeled using the Two-Moment Aerosol Sectional
(TOMAS) microphysics algorithm coupled to the GISS II-prime general
circulation model. The presence of organics affects CCN activity in
competing ways: by reducing the amount of solute available in the particle
and decreasing surface tension of CCN. To model surfactant effects, surface
tension depression data from seawater samples taken near the Georgia coast
were applied as a function of carbon concentrations. A global marine organic
aerosol emission rate of 17.7 Tg C yr−1 is estimated from the
simulations. Marine organics exert a localized influence on CCN(0.2%)
concentrations, decreasing regional concentrations by no more than 5% and
by less than 0.5% over most of the globe, assuming direct replacement of
sea salt aerosol with organic aerosol. The decrease in CCN concentrations
results from the fact that the decrease in particle solute concentration
outweighs the organic surfactant effects. The low sensitivity of
CCN(0.2%) to the marine organic emissions is likely due to the small
compositional changes: the mass fraction of OA in accumulation mode aerosol
increases by only ~15% in a biologically active region of the
Southern Ocean. To test the sensitivity to uncertainty in the sea spray
emissions process, we relax the assumption that sea spray aerosol number and
mass remain fixed and instead can add to sea spray emissions rather than
replace existing sea salt. In these simulations, we find that marine organic
aerosol can increase CCN by up to 50% in the Southern Ocean and 3.7%
globally during the austral summer. This vast difference in CCN impact
highlights the need for further observational exploration of the sea spray
aerosol emission process as well as evaluation and development of model
parameterizations. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|