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| Titel |
Quantifying sources of black carbon in western North America using observationally based analysis and an emission tagging technique in the Community Atmosphere Model |
| VerfasserIn |
R. Zhang, H. Wang, D. A. Hegg, Y. Qian, S. J. Doherty, C. Dang, P.-L. Ma, P. J. Rasch, Q. Fu |
| 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 ; 15, no. 22 ; Nr. 15, no. 22 (2015-11-18), S.12805-12822 |
| Datensatznummer |
250120169
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| Publikation (Nr.) |
 copernicus.org/acp-15-12805-2015.pdf |
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| Zusammenfassung |
| The Community Atmosphere Model (CAM5), equipped with a technique to tag
black carbon (BC) emissions by source regions and types, has been employed
to establish source–receptor relationships for atmospheric BC and its
deposition to snow over western North America. The CAM5 simulation was
conducted with meteorological fields constrained by reanalysis for year 2013
when measurements of BC in both near-surface air and snow are available for
model evaluation. We find that CAM5 has a significant low bias in predicted
mixing ratios of BC in snow but only a small low bias in predicted
atmospheric concentrations over northwestern USA and western Canada. Even with
a strong low bias in snow mixing ratios, radiative transfer calculations
show that the BC-in-snow darkening effect is substantially larger than the
BC dimming effect at the surface by atmospheric BC. Local sources contribute
more to near-surface atmospheric BC and to deposition than distant sources,
while the latter are more important in the middle and upper troposphere
where wet removal is relatively weak. Fossil fuel (FF) is the dominant
source type for total column BC burden over the two regions. FF is also the
dominant local source type for BC column burden, deposition, and
near-surface BC, while for all distant source regions combined the
contribution of biomass/biofuel (BB) is larger than FF. An observationally
based positive matrix factorization (PMF) analysis of the snow-impurity
chemistry is conducted to quantitatively evaluate the CAM5 BC source-type
attribution. While CAM5 is qualitatively consistent with the PMF analysis
with respect to partitioning of BC originating from BB and FF emissions, it
significantly underestimates the relative contribution of BB. In addition to
a possible low bias in BB emissions used in the simulation, the model is
likely missing a significant source of snow darkening from local soil found
in the observations. |
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