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| Titel |
Long-term trends of black carbon and sulphate aerosol in the Arctic: changes in atmospheric transport and source region emissions |
| VerfasserIn |
D. Hirdman, J. F. Burkhart, H. Sodemann, S. Eckhardt, A. Jefferson, P. K. Quinn, S. Sharma, J. Ström, A. Stohl |
| 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 (2010-10-05), S.9351-9368 |
| Datensatznummer |
250008805
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| Publikation (Nr.) |
 copernicus.org/acp-10-9351-2010.pdf |
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| Zusammenfassung |
As a part of the IPY project POLARCAT (Polar Study using Aircraft, Remote
Sensing, Surface Measurements and Models, of Climate, Chemistry, Aerosols
and Transport) and building on previous work (Hirdman et al., 2010), this
paper studies the long-term trends of both atmospheric transport as well as
equivalent black carbon (EBC) and sulphate for the three Arctic stations
Alert, Barrow and Zeppelin. We find a general downward trend in the measured
EBC concentrations at all three stations, with a decrease of −2.1±0.4 ng m−3 yr−1 (for the years 1989–2008) and −1.4±0.8 ng m−3 yr−1
(2002–2009) at Alert and Zeppelin respectively. The
decrease at Barrow is, however, not statistically significant. The measured
sulphate concentrations show a decreasing trend at Alert and Zeppelin of
−15±3 ng m−3 yr−1 (1985–2006) and −1.3±1.2 ng m−3 yr−1
(1990–2008) respectively, while there is no trend detectable at
Barrow.
To reveal the contribution of different source regions on these trends, we
used a cluster analysis of the output of the Lagrangian particle dispersion
model FLEXPART run backward in time from the measurement stations. We have
investigated to what extent variations in the atmospheric circulation,
expressed as variations in the frequencies of the transport from four source
regions with different emission rates, can explain the long-term trends in
EBC and sulphate measured at these stations. We find that the long-term
trend in the atmospheric circulation can only explain a minor fraction of
the overall downward trend seen in the measurements of EBC (0.3–7.2%) and
sulphate (0.3–5.3%) at the Arctic stations. The changes in emissions are
dominant in explaining the trends. We find that the highest EBC and sulphate
concentrations are associated with transport from Northern Eurasia and
decreasing emissions in this region drive the downward trends. Northern
Eurasia (cluster: NE, WNE and ENE) is the dominant emission source at all
Arctic stations for both EBC and sulphate during most seasons. In
wintertime, there are indications that the EBC emissions from the eastern
parts of Northern Eurasia (ENE cluster) have increased over the last decade. |
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