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| Titel |
Global modelling of direct and indirect effects of sea spray aerosol using a source function encapsulating wave state |
| VerfasserIn |
A.-I. Partanen, E. M. Dunne, T. Bergman, A. Laakso, H. Kokkola, J. Ovadnevaite, L. Sogacheva, D. Baisnée, J. Sciare, A. Manders, C. O'Dowd, G. de Leeuw, H. Korhonen |
| 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 ; 14, no. 21 ; Nr. 14, no. 21 (2014-11-07), S.11731-11752 |
| Datensatznummer |
250119145
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| Publikation (Nr.) |
 copernicus.org/acp-14-11731-2014.pdf |
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| Zusammenfassung |
| Recently developed parameterizations for the sea spray aerosol source flux, encapsulating wave
state, and its organic fraction were incorporated into the aerosol–climate model ECHAM-HAMMOZ to
investigate the direct and indirect radiative effects of sea spray aerosol particles. Our
simulated global sea salt emission of 805 Tg yr−1 (uncertainty range
378–1233 Tg yr−1) was much lower than typically found in previous studies. Modelled
sea salt and sodium ion concentrations agreed relatively well with measurements in the smaller
size ranges at Mace Head (annual normalized mean model bias −13% for particles with vacuum
aerodynamic diameter Dva < 1 μm), Point Reyes (−29% for particles
with aerodynamic diameter Da < 2.5 μm) and Amsterdam Island (−52%
for particles with Da < 1 μm) but the larger sizes were overestimated
(899% for particles with 2.5 μm < Da < 10 μm) at
Amsterdam Island. This suggests that at least the high end of the previous estimates of sea spray
mass emissions is unrealistic. On the other hand, the model clearly underestimated the observed
concentrations of organic or total carbonaceous aerosol at Mace Head (−82%) and Amsterdam
Island (−68%). The large overestimation (212%) of organic matter at Point Reyes was
due to the contribution of continental sources. At the remote Amsterdam Island site, the organic
concentration was underestimated especially in the biologically active months, suggesting a need
to improve the parameterization of the organic sea spray fraction. Globally, the
satellite-retrieved AOD over the oceans, using PARASOL data, was underestimated by the model
(means over ocean 0.16 and 0.10, respectively); however, in the pristine region around Amsterdam
Island the measured AOD fell well within the simulated uncertainty range. The simulated sea spray
aerosol contribution to the indirect radiative effect was positive (0.3 W m−2), in
contrast to previous studies. This positive effect was ascribed to the tendency of sea salt
aerosol to suppress both the in-cloud supersaturation and the formation of cloud condensation
nuclei from sulfate. These effects can be accounted for only in models with sufficiently detailed
aerosol microphysics and physics-based parameterizations of cloud activation. However, due to
a strong negative direct effect, the simulated effective radiative forcing (total radiative)
effect was −0.2 W m−2. The simulated radiative effects of the primary marine organic
emissions were small, with a direct effect of 0.03 W m−2 and an indirect effect of
−0.07 W m−2. |
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