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| Titel |
Black carbon in the Arctic: the underestimated role of gas flaring and residential combustion emissions |
| VerfasserIn |
A. Stohl, Z. Klimont, S. Eckhardt, K. Kupiainen, V. P. Shevchenko, V. M. Kopeikin, A. N. Novigatsky |
| 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 ; 13, no. 17 ; Nr. 13, no. 17 (2013-09-05), S.8833-8855 |
| Datensatznummer |
250085675
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| Publikation (Nr.) |
 copernicus.org/acp-13-8833-2013.pdf |
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| Zusammenfassung |
| Arctic haze is a seasonal phenomenon with high concentrations of
accumulation-mode aerosols occurring in the Arctic in winter and early
spring. Chemistry transport models and climate chemistry models struggle to
reproduce this phenomenon, and this has recently prompted changes in aerosol
removal schemes to remedy the modeling problems. In this paper, we show that
shortcomings in current emission data sets are at least as important. We
perform a 3 yr model simulation of black carbon (BC) with the Lagrangian
particle dispersion model FLEXPART. The model is driven with a new emission
data set ("ECLIPSE emissions") which includes emissions from gas flaring.
While gas flaring is estimated to contribute less than 3% of global BC
emissions in this data set, flaring dominates the estimated BC emissions in
the Arctic (north of 66° N). Putting these emissions into our
model, we find that flaring contributes 42% to the annual mean BC surface
concentrations in the Arctic. In March, flaring even accounts for 52% of all
Arctic BC near the surface. Most of the flaring BC remains close to the
surface in the Arctic, so that the flaring contribution to BC in the middle
and upper troposphere is small. Another important factor determining
simulated BC concentrations is the seasonal variation of BC emissions from
residential combustion (often also called domestic combustion, which is used
synonymously in this paper). We have calculated daily residential combustion
emissions using the heating degree day (HDD) concept based on ambient air
temperature and compare results from model simulations using emissions with
daily, monthly and annual time resolution. In January, the Arctic-mean
surface concentrations of BC due to residential combustion emissions are
150% higher when using daily emissions than when using annually constant
emissions. While there are concentration reductions in summer, they are
smaller than the winter increases, leading to a systematic increase of annual
mean Arctic BC surface concentrations due to residential combustion by 68%
when using daily emissions. A large part (93%) of this systematic increase
can be captured also when using monthly emissions; the increase is
compensated by a decreased BC burden at lower latitudes. In a comparison with
BC measurements at six Arctic stations, we find that using daily-varying
residential combustion emissions and introducing gas flaring emissions leads
to large improvements of the simulated Arctic BC, both in terms of mean
concentration levels and simulated seasonality. Case studies based on BC and
carbon monoxide (CO) measurements from the Zeppelin observatory appear to
confirm flaring as an important BC source that can produce pollution plumes
in the Arctic with a high BC / CO enhancement ratio, as expected for this
source type. BC measurements taken during a research ship cruise in the
White, Barents and Kara seas north of the region with strong flaring
emissions reveal very high concentrations of the order of
200–400 ng m−3. The model underestimates these concentrations
substantially, which indicates that the flaring emissions (and probably also
other emissions in northern Siberia) are rather under- than overestimated in
our emission data set. Our results suggest that it may not be "vertical
transport that is too strong or scavenging rates that are too low" and
"opposite biases in these processes" in the Arctic and elsewhere in current
aerosol models, as suggested in a recent review article (Bond et al.,
Bounding the role of black carbon in the climate system: a scientific
assessment, J. Geophys. Res., 2013), but missing emission sources and lacking
time resolution of the emission data that are causing opposite model biases
in simulated BC concentrations in the Arctic and in the mid-latitudes. |
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