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| Titel |
Explaining global surface aerosol number concentrations in terms of primary emissions and particle formation |
| VerfasserIn |
D. V. Spracklen, K. S. Carslaw, J. Merikanto, G. W. Mann, C. L. Reddington, S. Pickering, J. A. Ogren, E. Andrews, U. Baltensperger, E. Weingärtner, M. Boy, M. Kulmala  , L. Laakso, H. Lihavainen, N. Kivekäs, M. Komppula, N. Mihalopoulos, G. Kouvarakis, S. G. Jennings, C. O'Dowd, W. Birmili, A. Wiedensohler, R. Weller, J. Gras, P. Laj, K. Sellegri, B. Bonn, R. Krejci, A. Laaksonen, A. Hamed, A. Minikin, R. M. Harrison, R. Talbot, J. Sun |
| 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. 10 ; Nr. 10, no. 10 (2010-05-26), S.4775-4793 |
| Datensatznummer |
250008476
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| Publikation (Nr.) |
 copernicus.org/acp-10-4775-2010.pdf |
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| Zusammenfassung |
| We synthesised observations of total particle number (CN)
concentration from 36 sites around the world.
We found that annual mean
CN concentrations are typically 300–2000 cm−3 in the
marine boundary layer and free troposphere (FT) and 1000–10 000 cm−3 in the continental boundary layer (BL). Many sites
exhibit pronounced seasonality with summer time concentrations a
factor of 2–10 greater than wintertime concentrations. We used
these CN observations to evaluate primary and secondary sources of
particle number in a global aerosol microphysics model. We found
that emissions of primary particles can reasonably reproduce the
spatial pattern of observed CN concentration (R2=0.46)
but fail to explain the observed seasonal cycle
(R2=0.1). The modeled CN concentration in the FT was
biased low (normalised mean bias, NMB=−88%) unless
a secondary source of particles was included, for example from
binary homogeneous nucleation of sulfuric acid and water
(NMB=−25%). Simulated CN concentrations in the
continental BL were also biased low (NMB=−74%)
unless the number emission of anthropogenic primary particles was
increased or a mechanism that results in particle formation in
the BL was included. We ran a number of simulations where we
included an empirical BL nucleation mechanism either using the
activation-type mechanism (nucleation rate, J, proportional to
gas-phase sulfuric acid concentration to the power one) or
kinetic-type mechanism (J proportional to sulfuric acid to the
power two) with a range of nucleation coefficients. We found
that the seasonal CN cycle observed at continental BL sites was
better simulated by BL particle formation (R2=0.3) than
by increasing the number emission from primary anthropogenic
sources (R2=0.18). The nucleation constants that resulted
in best overall match between model and observed CN
concentrations were consistent with values derived in previous studies from detailed
case studies at individual sites. In our model, kinetic and
activation-type nucleation parameterizations gave similar
agreement with observed monthly mean CN concentrations. |
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