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| Titel |
Enhancement of marine cloud albedo via controlled sea spray injections: a global model study of the influence of emission rates, microphysics and transport |
| VerfasserIn |
H. Korhonen, K. S. Carslaw, S. Romakkaniemi |
| 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 ; 10, no. 9 ; Nr. 10, no. 9 (2010-05-03), S.4133-4143 |
| Datensatznummer |
250008419
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| Publikation (Nr.) |
 copernicus.org/acp-10-4133-2010.pdf |
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| Zusammenfassung |
| Modification of cloud albedo by controlled emission of sea spray particles
into the atmosphere has been suggested as a possible geoengineering option
to slow global warming. Previous global studies have imposed changes in
cloud drop concentration in low level clouds to explore the radiative and
climatic effects. Here, we use a global aerosol transport model to quantify
how an imposed flux of sea spray particles affects the natural aerosol
processes, the particle size distribution, and concentrations of cloud
drops. We assume that the proposed fleet of vessels emits sea spray
particles with a wind speed-dependent flux into four regions of persistent
stratocumulus cloud off the western coasts of continents. The model results
show that fractional changes in cloud drop number concentration (CDNC) vary
substantially between the four regions because of differences in wind speed
(which affects the spray efficiency of the vessels), transport and particle
deposition rates, and because of variations in aerosols from natural and
anthropogenic sources. Using spray emission rates comparable to those
implied by previous studies we find that the predicted CDNC changes are very
small (maximum 20%) and in one of the four regions even negative. The
weak or negative effect is because the added particles suppress the in-cloud
supersaturation and prevent existing aerosol particles from forming cloud
drops. A scenario with five times higher emissions (considerably higher than
previously assumed) increases CDNC on average by 45–163%, but median
concentrations are still below the 375 cm−3 assumed in previous
studies. An inadvertent effect of the spray emissions is that sulphur
dioxide concentrations are suppressed by 1–2% in the seeded regions and
sulphuric acid vapour by 64–68% due to chemical reactions on the
additional salt particles. The impact of this suppression on existing
aerosol is negligible in the model, but should be investigated further in
the real environment so that inadvertent impacts can be excluded. |
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