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| Titel |
Aircraft observations of enhancement and depletion of black carbon mass in the springtime Arctic |
| VerfasserIn |
J. R. Spackman, R. S. Gao, W. D. Neff, J. P. Schwarz, L. A. Watts, D. W. Fahey, J. S. Holloway, T. B. Ryerson, J. Peischl, 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 ; 10, no. 19 ; Nr. 10, no. 19 (2010-10-12), S.9667-9680 |
| Datensatznummer |
250008826
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| Publikation (Nr.) |
 copernicus.org/acp-10-9667-2010.pdf |
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| Zusammenfassung |
| Understanding the processes controlling black carbon (BC) in the Arctic is
crucial for evaluating the impact of anthropogenic and natural sources of BC
on Arctic climate. Vertical profiles of BC mass loadings were observed from
the surface to near 7-km altitude in April 2008 using a Single-Particle Soot
Photometer (SP2) during flights on the NOAA WP-3D research aircraft from
Fairbanks, Alaska. These measurements were conducted during the
NOAA-sponsored Aerosol, Radiation, and Cloud Processes affecting Arctic
Climate (ARCPAC) project. In the free troposphere, the Arctic air mass was
influenced by long-range transport from biomass-burning and anthropogenic
source regions at lower latitudes especially during the latter part of the
campaign. Average BC mass mixing ratios peaked at about 150 ng BC (kg dry air )−1 near 5.5 km altitude in the aged Arctic air
mass and 250 ng kg−1 at 4.5 km in biomass-burning influenced air. BC mass loadings were
enhanced by up to a factor of 5 in biomass-burning influenced air compared to the aged
Arctic air mass. At the bottom of some of the profiles, positive vertical
gradients in BC were observed over the sea-ice. The vertical profiles
generally occurred in the vicinity of open leads in the sea-ice. In the aged
Arctic air mass, BC mass loadings more than doubled with increasing altitude
within the ABL and across the boundary layer transition while carbon
monoxide (CO) remained constant. This is evidence for depletion of BC mass
in the ABL. BC mass loadings were positively correlated with O3 in
ozone depletion events (ODEs) for all the observations in the ABL. Since
bromine catalytically destroys ozone in the ABL after being released as
molecular bromine in regions of new sea-ice formation at the surface, the
BC–O3 correlation suggests that BC particles were removed by a surface
process such as dry deposition. We develop a box model to estimate the dry
deposition flux of BC mass to the snow constrained by the vertical profiles
of BC mass in the ABL. Open leads in the sea-ice may increase vertical
mixing and entrainment of pollution from the free troposphere possibly
enhancing the deposition of BC aerosol to the snow. |
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