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| Titel |
The influence of foreign vs. North American emissions on surface ozone in the US |
| VerfasserIn |
D. R. Reidmiller, A. M. Fiore, D. A. Jaffe, D. Bergmann, C. Cuvelier, F. J. Dentener, B. N. Duncan, G. Folberth, M. Gauss, S. Gong, P. Hess, J. E. Jonson, T. Keating, A. Lupu, E. Marmer, R. Park, M. G. Schultz, D. T. Shindell  , S. Szopa, M. G. Vivanco, O. Wild, A. Zuber |
| 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 ; 9, no. 14 ; Nr. 9, no. 14 (2009-07-27), S.5027-5042 |
| Datensatznummer |
250007530
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| Publikation (Nr.) |
 copernicus.org/acp-9-5027-2009.pdf |
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| Zusammenfassung |
| As part of the Hemispheric Transport of Air Pollution (HTAP;
http:// www.htap.org) project, we analyze results from 15 global and
1 hemispheric chemical transport models and compare these to Clean Air Status
and Trends Network (CASTNet) observations in the United States (US) for 2001.
Using the policy-relevant maximum daily 8-h average ozone (MDA8 O3)
statistic, the multi-model ensemble represents the observations well (mean
r2=0.57, ensemble bias = +4.1 ppbv for all US regions and all
seasons) despite a wide range in the individual model results. Correlations
are strongest in the northeastern US during spring and fall (r2=0.68);
and weakest in the midwestern US in summer (r2=0.46). However, large
positive mean biases exist during summer for all eastern US regions, ranging
from 10–20 ppbv, and a smaller negative bias is present in the western US
during spring (~3 ppbv). In nearly all other regions and seasons, the
biases of the model ensemble simulations are ≤5 ppbv. Sensitivity
simulations in which anthropogenic O3-precursor emissions
(NOx + NMVOC + CO + aerosols) were decreased by 20% in four source
regions: East Asia (EA), South Asia (SA), Europe (EU) and North America (NA)
show that the greatest response of MDA8 O3 to the summed foreign emissions
reductions occurs during spring in the West (0.9 ppbv reduction due to 20%
emissions reductions from EA + SA + EU). East Asia is the largest
contributor to MDA8 O3 at all ranges of the O3 distribution for most
regions (typically ~0.45 ppbv) followed closely by Europe. The
exception is in the northeastern US where emissions reductions in EU had a
slightly greater influence than EA emissions, particularly in the middle of
the MDA8 O3 distribution (response of ~0.35 ppbv between
35–55 ppbv). EA and EU influences are both far greater (about 4x)
than that from SA in all regions and seasons. In all regions and seasons
O3-precursor emissions reductions of 20% in the NA source region decrease
MDA8 O3 the most – by a factor of 2 to nearly 10 relative to foreign
emissions reductions. The O3 response to anthropogenic NA emissions is
greatest in the eastern US during summer at the high end of the O3
distribution (5–6 ppbv for 20% reductions). While the impact of foreign
emissions on surface O3 in the US is not negligible – and is of
increasing concern given the recent growth in Asian emissions – domestic
emissions reductions remain a far more effective means of decreasing
MDA8 O3 values, particularly those above 75 ppb (the current US
standard). |
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