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| Titel |
Observations and modeling of air quality trends over 1990–2010 across the Northern Hemisphere: China, the United States and Europe |
| VerfasserIn |
J. Xing, R. Mathur, J. Pleim, C. Hogrefe, C.-M. Gan, D. C. Wong, C. Wei, R. Gilliam, G. Pouliot |
| 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. 5 ; Nr. 15, no. 5 (2015-03-10), S.2723-2747 |
| Datensatznummer |
250119511
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| Publikation (Nr.) |
 copernicus.org/acp-15-2723-2015.pdf |
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| Zusammenfassung |
Trends in air quality across the Northern Hemisphere over a 21-year period
(1990–2010) were simulated using the Community Multiscale Air
Quality (CMAQ) multiscale chemical transport
model driven by meteorology from Weather Research and Forecasting (WRF) simulations and internally consistent
historical emission inventories obtained from EDGAR. Thorough comparison
with several ground observation networks mostly over Europe and North
America was conducted to evaluate the model performance as well as the
ability of CMAQ to reproduce the observed trends in air quality over the
past 2 decades in three regions: eastern China, the continental United
States and Europe.
The model successfully reproduced the observed decreasing trends in
SO2, NO2, 8 h O3 maxima, SO42− and elemental carbon (EC) in the US
and Europe. However, the model fails to reproduce the decreasing trends in
NO3− in the US, potentially pointing to uncertainties of NH3
emissions. The model failed to capture the 6-year trends of SO2 and
NO2 in CN-API (China – Air
Pollution Index) from 2005 to 2010, but reproduced the observed pattern of
O3 trends shown in three World Data Centre for Greenhouse Gases (WDCGG) sites over eastern Asia. Due to the
coarse spatial resolution employed in these calculations, predicted SO2
and NO2 concentrations are underestimated relative to all urban
networks, i.e., US-AQS (US – Air Quality System; normalized mean bias (NMB) = −38% and −48%), EU-AIRBASE
(European Air quality data Base; NMB = −18 and −54%) and CN-API (NMB = −36 and −68%).
Conversely, at the rural network EU-EMEP (European Monitoring
and Evaluation Programme), SO2 is overestimated (NMB from
4 to 150%) while NO2 is simulated well (NMB within ±15%)
in all seasons. Correlations between simulated and observed O3 wintertime daily 8 h maxima (DM8) are poor compared to other seasons for
all networks. Better correlation between simulated and observed
SO42− was found compared to that for SO2. Underestimation of
summer SO42− in the US may be associated with the uncertainty in
precipitation and associated wet scavenging representation in the model. The
model exhibits worse performance for NO3− predictions,
particularly in summer, due to high uncertainties in the gas/particle
partitioning of NO3− as well as seasonal variations of NH3
emissions. There are high correlations (R > 0.5) between observed
and simulated EC, although the model underestimates the EC concentration by
65% due to the coarse grid resolution as well as uncertainties in the PM
speciation profile associated with EC emissions.
The almost linear response seen in the trajectory of modeled O3 changes
in eastern China over the past 2 decades suggests that control
strategies that focus on combined control of NOx and volatile organic compound (VOC) emissions with
a ratio of 0.46 may provide the most effective means for O3 reductions
for the region devoid of nonlinear response potentially associated with
NOx or VOC limitation resulting from alternate strategies. The response
of O3 is more sensitive to changes in NOx emissions in the eastern
US because the relative abundance of biogenic VOC emissions tends to reduce
the effectiveness of VOC controls. Increasing NH3 levels offset the
relative effectiveness of NOx controls in reducing the relative
fraction of aerosol NO3− formed from declining NOx emissions
in the eastern US, while the control effectiveness was assured by the
simultaneous control of NH3 emission in Europe. |
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