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| Titel |
Summertime weekly cycles of observed and modeled NOx and O3 concentrations as a function of satellite-derived ozone production sensitivity and land use types over the Continental United States |
| VerfasserIn |
Y. Choi, H. Kim, D. Tong, P. Lee |
| 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 ; 12, no. 14 ; Nr. 12, no. 14 (2012-07-19), S.6291-6307 |
| Datensatznummer |
250011328
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| Publikation (Nr.) |
 copernicus.org/acp-12-6291-2012.pdf |
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| Zusammenfassung |
| To show how remote-sensing products can be used to classify the entire CONUS
domain into "geographical regions" and "chemical regimes", we analyzed
the results of simulation from the Community Multiscale Air Quality (CMAQ)
model version 4.7.1 over the Conterminous United States (CONUS) for August
2009. In addition, we observe how these classifications capture the weekly
cycles of ground-level nitrogen oxide (NOx) and ozone (O3) at
US EPA Air Quality System (AQS) sites. We use the Advanced Very High
Resolution Radiometer (AVHRR) land use dominant categories and the Global
Ozone Monitoring Experiment-2 (GOME-2) HCHO/NO2 column density ratios to
allocate geographical regions (i.e., "urban", "forest", and "other"
regions) and chemical regimes (i.e., "NOx-saturated", "NOx-sensitive",
and "mixed" regimes). We also show that CMAQ simulations using GOME-2
satellite-adjusted NOx emissions mitigate the discrepancy between
the weekly cycles of NOx from AQS observations and that from CMAQ
simulation results. We found geographical regions and chemical regimes do not
show a one-to-one correspondence: the averaged HCHO / NO2 ratios for AVHRR
"urban" and "forest" regions are 2.1 and 4.0, which correspond to GOME-2
"mixed" and "NOx-sensitive" regimes, respectively. Both AQS-observed and
CMAQ-simulated weekly cycles of NOx show high concentrations on
weekdays and low concentrations on weekends, but with one- or two-day shifts
of weekly high peaks in the simulated results, which eventually introduces
the shifts in simulated weekly-low O3 concentration. In addition,
whereas the high weekend O3 anomaly is clearly observable at sites over
the GOME-2 NOx-saturated regime in both AQS and CMAQ, the weekend
effect is not captured at sites over the AVHRR urban region because of the
chemical characteristics of the urban sites (≈GOME-2 mixed
regime). In addition, the weekend effect from AQS is more clearly discernible
at sites above the GOME-2 NOx-saturated regime than at other sites
above the CMAQ NOx-saturated regime, suggesting that the
GOME-2-based chemical regime classification is more accurate than CMAQ-based
chemical classification. Furthermore, the CMAQ simulations using the
GOME-2-derived NOx emissions adjustment (decreasing from 462 Gg N
to 426 Gg N over the US for August 2009) show large reductions of simulated
NOx concentrations (particularly over the urban, or
NOx-saturated, regime), and mitigates the large discrepancies
between the absolute amount and the weekly pattern of NOx
concentrations of the EPA AQS and those of the baseline CMAQ. |
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