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| Titel |
Multi-model study of chemical and physical controls on transport of anthropogenic and biomass burning pollution to the Arctic |
| VerfasserIn |
S. A. Monks, S. R. Arnold, L. K. Emmons, K. S. Law, S. Turquety, B. N. Duncan, J. Flemming, V. Huijnen, S. Tilmes, J. Langner, J. Mao, Y. Long, J. L. Thomas, S. D. Steenrod, J. C. Raut, C. Wilson, M. P. Chipperfield, G. S. Diskin, A. Weinheimer, H. Schlager, G. Ancellet |
| 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. 6 ; Nr. 15, no. 6 (2015-03-31), S.3575-3603 |
| Datensatznummer |
250119590
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| Publikation (Nr.) |
 copernicus.org/acp-15-3575-2015.pdf |
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| Zusammenfassung |
Using observations from aircraft, surface stations and a satellite instrument, we
comprehensively evaluate multi-model simulations of carbon monoxide (CO) and
ozone (O3) in the Arctic and over lower latitude emission regions, as part
of the POLARCAT Model Inter-comparison Project (POLMIP). Evaluation of 11-
atmospheric models with chemistry shows that they generally underestimate CO
throughout the Arctic troposphere, with the largest biases found during
winter and spring. Negative CO biases are also found throughout the Northern
Hemisphere, with multi-model mean gross errors (9–12%) suggesting models
perform similarly over Asia, North America and Europe. A multi-model annual
mean tropospheric OH (10.8 ± 0.6 × 105 molec cm−3)
is found to be slightly higher than previous estimates of OH constrained by
methyl chloroform, suggesting negative CO biases in models may be improved
through better constraints on OH. Models that have lower Arctic OH do not
always show a substantial improvement in their negative CO biases, suggesting
that Arctic OH is not the dominant factor controlling the Arctic CO burden in
these models. In addition to these general biases, models do not capture the
magnitude of CO enhancements observed in the Arctic free troposphere in
summer, suggesting model errors in the simulation of plumes that are
transported from anthropogenic and biomass burning sources at lower
latitudes. O3 in the Arctic is also generally underestimated, particularly
at the surface and in the upper troposphere. Summer O3 comparisons over
lower latitudes show several models overestimate upper tropospheric
concentrations.
Simulated CO, O3 and OH all demonstrate a substantial degree of
inter-model variability. Idealised CO-like tracers are used to quantitatively
compare the impact of inter-model differences in transport and OH on CO in
the Arctic troposphere. The tracers show that model differences in transport
from Europe in winter and from Asia throughout the year are important sources
of model variability at Barrow. Unlike transport, inter-model variability in
OH similarly affects all regional tracers at Barrow. Comparisons of fixed-lifetime
and OH-loss idealised CO-like tracers throughout the Arctic
troposphere show that OH differences are a much larger source of inter-model
variability than transport differences. Model OH concentrations are
correlated with H2O concentrations, suggesting water vapour concentrations
are linked to differences in simulated concentrations of CO and OH at high
latitudes in these simulations. Despite inter-model differences in transport
and OH, the relative contributions from the different source regions (North
America, Europe and Asia) and different source types (anthropogenic and
biomass burning) are comparable across the models. Fire emissions from the
boreal regions in 2008 contribute 33, 43 and 19% to the total Arctic
CO-like tracer in spring, summer and autumn, respectively, highlighting the
importance of boreal fire emissions in controlling pollutant burdens in the
Arctic. |
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