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| Titel |
A global process-based study of marine CCN trends and variability |
| VerfasserIn |
E. M. Dunne, S. Mikkonen, H. Kokkola, 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. 24 ; Nr. 14, no. 24 (2014-12-19), S.13631-13642 |
| Datensatznummer |
250119257
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| Publikation (Nr.) |
 copernicus.org/acp-14-13631-2014.pdf |
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| Zusammenfassung |
| Low-level clouds have a strong climate-cooling effect in oceanic
regions due to the much lower albedo of the underlying sea
surface. Marine clouds typically have low droplet concentrations,
making their radiative properties susceptible to changes in cloud
condensation nucleus (CCN) concentrations. Here, we use the global
aerosol model GLOMAP to investigate the processes that determine
variations in marine CCN concentrations, and focus especially on the
effects of previously identified wind speed trends in recent
decades. Although earlier studies have found a link between linear
wind speed trends and CCN concentration, we find that the effects of
wind speed trends identified using a dynamic linear model in the
Northern Equatorial Pacific (0.56 m s−1 per decade in the
period 1990–2004) and the North Atlantic (−0.21 m s−1
per decade) are largely dampened by other processes controlling the
CCN concentration, namely nucleation scavenging and transport of
continental pollution. A CCN signal from wind speed change is seen
only in the most pristine of the studied regions, i.e. over the
Southern Ocean, where we simulate 3.4 cm−3 and
0.17 m s−1 increases over the 15-year period in the
statistical mean levels of CCN and wind speed, respectively. Our
results suggest that future changes in wind-speed-driven aerosol
emissions from the oceans can probably have a climate feedback via
clouds only in the most pristine regions. On the other hand,
a feedback mechanism via changing precipitation patterns and
intensities could take place over most oceanic regions, as we have
shown that nucleation scavenging has by far the largest absolute
effect on CCN concentrations. |
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