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| Titel |
On the observed response of ozone to NOx and VOC reactivity reductions in San Joaquin Valley California 1995–present |
| VerfasserIn |
S. E. Pusede, R. C. Cohen |
| 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. 18 ; Nr. 12, no. 18 (2012-09-17), S.8323-8339 |
| Datensatznummer |
250011449
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| Publikation (Nr.) |
 copernicus.org/acp-12-8323-2012.pdf |
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| Zusammenfassung |
| We describe the effects of nitrogen oxide (NOx) and organic
reactivity reductions on the frequency of high ozone days in California's San
Joaquin Valley. We use sixteen years of observations of ozone, nitrogen
oxides, and temperature at sites upwind, within, and downwind of three cities
to assess the probability of exceeding the California 8-h average ozone
standard of 70.4 ppb at each location. The comprehensive data records in the
region and the steep decreases in emissions over the last decade are
sufficient to constrain the relative import of NOx and organic
reactivity reductions on the frequency of violations. We show that high ozone
has a large component that is due to local production, as the probability of
exceeding the state standard is lowest for each city at the upwind site,
increases in the city center, is highest at downwind locations, and then
decreases at the receptor city to the south. We see that reductions in
organic reactivity have been very effective in the central and northern
regions of the San Joaquin but less so in the southern portion of the Valley.
We find evidence for two distinct categories of reactivity sources: one
source that has decreased and dominates at moderate temperatures, and a
second source that dominates at high temperatures, particularly in the
southern San Joaquin, and has not changed over the last twelve years. We show
that NOx reductions are already effective or are poised to become so
in the southern and central Valley, where violations are most frequent, as
conditions in these regions have or are transitioning to NOx-limited
chemistry when temperatures are hottest and high ozone most probable. |
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