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| Titel |
The direct and indirect radiative effects of biogenic secondary organic aerosol |
| VerfasserIn |
C. E. Scott, A. Rap, D. V. Spracklen, P. M. Forster, K. S. Carslaw, G. W. Mann, K. J. Pringle, N. Kivekäs, M. Kulmala  , H. Lihavainen, P. Tunved |
| 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. 1 ; Nr. 14, no. 1 (2014-01-14), S.447-470 |
| Datensatznummer |
250118263
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| Publikation (Nr.) |
 copernicus.org/acp-14-447-2014.pdf |
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| Zusammenfassung |
| We use a global aerosol microphysics model in combination with an offline
radiative transfer model to quantify the radiative effect of biogenic
secondary organic aerosol (SOA) in the present-day atmosphere. Through its
role in particle growth and ageing, the presence of biogenic SOA increases
the global annual mean concentration of cloud condensation nuclei (CCN; at
0.2% supersaturation) by 3.6–21.1%, depending upon the yield of SOA
production from biogenic volatile organic compounds (BVOCs), and the nature
and treatment of concurrent primary carbonaceous emissions. This increase in
CCN causes a rise in global annual mean cloud droplet number concentration
(CDNC) of 1.9–5.2%, and a global mean first aerosol indirect effect (AIE)
of between +0.01 W m−2 and −0.12 W m−2. The radiative impact of
biogenic SOA is far greater when biogenic oxidation products also contribute
to the very early stages of new particle formation; using two
organically mediated mechanisms for new particle formation, we simulate
global annual mean first AIEs of −0.22 W m−2 and −0.77 W m−2. The
inclusion of biogenic SOA substantially improves the simulated seasonal
cycle in the concentration of CCN-sized particles observed at three forested
sites. The best correlation is found when the organically mediated
nucleation mechanisms are applied, suggesting that the first AIE of biogenic
SOA could be as large as −0.77 W m−2. The radiative impact of SOA is
sensitive to the presence of anthropogenic emissions. Lower background
aerosol concentrations simulated with anthropogenic emissions from 1750 give
rise to a greater fractional CCN increase and a more substantial first AIE
from biogenic SOA. Consequently, the anthropogenic indirect radiative
forcing between 1750 and the present day is sensitive to assumptions about
the amount and role of biogenic SOA. We also calculate an annual global mean
direct radiative effect of between −0.08 W m−2 and −0.78 W m−2 in
the present day, with uncertainty in the amount of SOA produced from the
oxidation of BVOCs accounting for most of this range. |
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