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| Titel |
Absorbing aerosol in the troposphere of the Western Arctic during the 2008 ARCTAS/ARCPAC airborne field campaigns |
| VerfasserIn |
C. S. McNaughton, A. D. Clarke, S. Freitag, V. N. Kapustin, Y. Kondo, N. Moteki, L. Sahu, N. Takegawa, J. P. Schwarz, J. R. Spackman, L. Watts, G. Diskin, J. Podolske, J. S. Holloway, A. Wisthaler, T. Mikoviny, J. Gouw, C. Warneke, J. Jimenez, M. Cubison, S. G. Howell, A. Middlebrook, R. Bahreini, B. E. Anderson, E. Winstead, K. L. Thornhill, D. Lack, J. Cozic, C. A. Brock |
| 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 ; 11, no. 15 ; Nr. 11, no. 15 (2011-08-01), S.7561-7582 |
| Datensatznummer |
250009962
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| Publikation (Nr.) |
 copernicus.org/acp-11-7561-2011.pdf |
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| Zusammenfassung |
| In the spring of 2008 NASA and NOAA funded the ARCTAS and ARCPAC field
campaigns as contributions to POLARCAT, a core IPY activity. During the
campaigns the NASA DC-8, P-3B and NOAA WP-3D aircraft conducted over 160 h
of in-situ sampling between 0.1 and 12 km throughout the Western Arctic
north of 55° N (i.e. Alaska to Greenland). All aircraft were
equipped with multiple wavelength measurements of aerosol optics, trace gas
and aerosol chemistry measurements, as well as direct measurements of the
aerosol size distributions and black carbon mass. Late April of 2008 proved
to be exceptional in terms of Asian biomass burning emissions transported to
the Western Arctic. Though these smoke plumes account for only 11–14 % of
the samples within the Western Arctic domain, they account for 42–47 % of
the total burden of black carbon. Dust was also commonly observed but only
contributes to 4–12 % and 3–8 % of total light absorption at 470 and
530 nm wavelengths above 6 km. Below 6 km, light absorption by
carbonaceous aerosol derived from urban/industrial and biomass burning
emissions account for 97–99 % of total light absorption by aerosol.
Stratifying the data to reduce the influence of dust allows us to determine
mass absorption efficiencies for black carbon of 11.2±0.8, 9.5±0.6
and 7.4±0.7 m2 g−1 at 470, 530 and 660 nm wavelengths. These
estimates are consistent with 35–80 % enhancements in 530 nm absorption
due to clear or slightly absorbing coatings of pure black carbon particulate.
Assuming a 1/λ wavelength dependence for BC absorption, and assuming
that refractory aerosol (420 °C, τ = 0.1 s) in low-dust
samples is dominated by brown carbon, we derive mass absorption efficiencies
for brown carbon of 0.83±0.15 and 0.27±0.08 m2 g−1 at 470
and 530 nm wavelengths. Estimates for the mass absorption efficiencies of
Asian dust are 0.034 m2 g−1 and 0.017 m2 g−1. However
the absorption efficiency estimates for dust are highly uncertain due to the
limitations imposed by PSAP instrument noise. In-situ ARCTAS/ARCPAC
measurements during the IPY provide valuable constraints for absorbing
aerosol over the Western Arctic, species which are currently poorly simulated
over a region that is critically under-sampled. |
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