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| Titel |
Global distribution and climate forcing of marine organic aerosol: 1. Model improvements and evaluation |
| VerfasserIn |
N. Meskhidze, J. Xu, B. Gantt, Y. Zhang, A. Nenes, S. J. Ghan, X. Liu, R. Easter, R. Zaveri |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 22 ; Nr. 11, no. 22 (2011-11-23), S.11689-11705 |
| Datensatznummer |
250010214
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| Publikation (Nr.) |
 copernicus.org/acp-11-11689-2011.pdf |
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| Zusammenfassung |
| Marine organic aerosol emissions have been implemented and evaluated within
the National Center of Atmospheric Research (NCAR)'s Community Atmosphere
Model (CAM5) with the Pacific Northwest National Laboratory's 7-mode Modal
Aerosol Module (MAM-7). Emissions of marine primary organic aerosols (POA),
phytoplankton-produced isoprene- and monoterpenes-derived secondary organic
aerosols (SOA) and methane sulfonate (MS−) are shown to affect surface
concentrations of organic aerosols in remote
marine regions. Global emissions of submicron marine POA is estimated to be
7.9 and 9.4 Tg yr−1, for the Gantt et al. (2011) and Vignati et al. (2010)
emission parameterizations, respectively. Marine sources of SOA and
particulate MS− (containing both sulfur and carbon atoms) contribute an additional 0.2 and
5.1 Tg yr−1, respectively. Widespread areas over productive waters of
the Northern Atlantic, Northern Pacific, and the Southern Ocean show
marine-source submicron organic aerosol surface concentrations of 100 ng m−3,
with values up to 400 ng m−3 over biologically productive
areas. Comparison of long-term surface observations of water insoluble
organic matter (WIOM) with POA concentrations from the two emission
parameterizations shows that despite revealed discrepancies (often more than
a factor of 2), both Gantt et al. (2011) and Vignati et al. (2010)
formulations are able to capture the magnitude of marine organic aerosol
concentrations, with the Gantt et al. (2011) parameterization attaining
better seasonality. Model simulations show that the mixing state of the
marine POA can impact the surface number concentration of cloud condensation
nuclei (CCN). The largest increases (up to 20%) in CCN (at a
supersaturation (S) of 0.2%) number concentration are obtained over
biologically productive ocean waters when marine organic aerosol is assumed
to be externally mixed with sea-salt. Assuming marine organics are
internally-mixed with sea-salt provides diverse results with increases and
decreases in the concentration of CCN over different parts of the ocean. The
sign of the CCN change due to the addition of marine organics to sea-salt
aerosol is determined by the relative significance of the increase in mean
modal diameter due to addition of mass, and the decrease in particle
hygroscopicity due to compositional changes in marine aerosol. Based on
emerging evidence for increased CCN concentration over biologically active
surface ocean areas/periods, our study suggests that treatment of sea spray
in global climate models (GCMs) as an internal mixture of marine organic
aerosols and sea-salt will likely lead to an underestimation in CCN number
concentration. |
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