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| Titel |
Uncertainty in global CCN concentrations from uncertain aerosol nucleation and primary emission rates |
| VerfasserIn |
J. R. Pierce, P. J. Adams |
| 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 ; 9, no. 4 ; Nr. 9, no. 4 (2009-02-19), S.1339-1356 |
| Datensatznummer |
250006930
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| Publikation (Nr.) |
 copernicus.org/acp-9-1339-2009.pdf |
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| Zusammenfassung |
| The indirect effect of aerosols on climate is highly uncertain
and limits our ability to assess anthropogenic climate change. The foundation of
this uncertainty is uncertainty in the number of cloud condensation nuclei
(CCN), which itself stems from uncertainty in aerosol nucleation, primary
emission and growth rates. In this paper, we use a global general circulation
model with aerosol microphysics to assess how the uncertainties in aerosol
nucleation, emission and growth rates affect our prediction of CCN(0.2%)
concentrations. Using several nucleation rate parameterizations that span six
orders of magnitude of globally averaged nucleation rates, the tropospheric
average CCN(0.2%) concentrations vary by 17% and the boundary layer average
vary by 12%. This sensitivity of tropospheric average CCN(0.2%) to the
nucleation parameterizations increases to 33% and 20% when the total primary
emissions are reduced by a factor of 3 and the SOA condensation rates are
increased by a factor of 3.5, respectively. These results show that it is
necessary to better understand global nucleation rates when determining CCN
concentrations. When primary emissions rates are varied by a factor of 3 while
using a binary nucleation parameterization, tropospheric average
CCN(0.2%) concentrations also vary by 17%, but boundary layer average vary by
40%. Using the fastest nucleation rate parameterization, these changes drop to
3% and 22%, respectively. These results show the importance of reducing
uncertainties in primary emissions, which appear from these results to be
somewhat more important for CCN than the much larger uncertainties in
nucleation. These results also show that uncertainties in nucleation and primary
emissions are more important when sufficient condensable material is available
to grow them to CCN sizes. The percent change in CCN(0.2%) concentration
between pre-industrial times and present day does not depend greatly on the
nucleation rate parameterization used for our base case scenarios; however,
because other factors, such as primary emissions and SOA, are uncertain in both
time periods, this may be a coincidence. |
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