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| Titel |
Changes of daily surface ozone maxima in Switzerland in all seasons from 1992 to 2002 and discussion of summer 2003 |
| VerfasserIn |
C. Ordóñez, H. Mathis, M. Furger, S. Henne, C. Hüglin, J. Staehelin, A. S. H. Prévôt |
| 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 ; 5, no. 5 ; Nr. 5, no. 5 (2005-05-25), S.1187-1203 |
| Datensatznummer |
250002804
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| Publikation (Nr.) |
 copernicus.org/acp-5-1187-2005.pdf |
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| Zusammenfassung |
| An Analysis of Covariance (ANCOVA) was used to derive the
influence of the meteorological variability on the daily maximum
ozone concentrations at 12 low-elevation sites north of the Alps
in Switzerland during the four seasons in the 1992–2002 period.
The afternoon temperature and the morning global radiation were
the variables that accounted for most of the meteorological
variability in summer and spring, while other variables that can
be related to vertical mixing and dilution of primary pollutants
(afternoon global radiation, wind speed, stability or day of the
week) were more significant in winter. In addition, the number of
days after a frontal passage was important to account for ozone
build-up in summer and ozone destruction in winter. The
statistical model proved to be a robust tool for reducing the
impact of the meteorological variability on the ozone
concentrations. The explained variance of the model, averaged over
all stations, ranged from 60.2% in winter to 71.9% in
autumn. The year-to-year variability of the seasonal medians of
daily ozone maxima was reduced by 85% in winter, 60% in
summer, and 50% in autumn and spring after the meteorological
adjustment. For most stations, no significantly negative trends
(at the 95% confidence level) of the summer medians of daily
O3 or Ox (O3+NO2) maxima were found
despite the significant reduction in the precursor emissions in
Central Europe. However, significant downward trends in the summer
90th percentiles of daily Ox maxima were
observed at 6 sites in the region around Zürich (on average
−0.73 ppb yr-1 for those sites). The lower effect of the
titration by NO as a consequence of the reduced emissions could
partially explain the significantly positive O3 trends in the
cold seasons (on average 0.69 ppb yr-1 in winter and 0.58 ppb
yr-1 in autumn). The increase of Ox found for most
stations in autumn (on average 0.23 ppb yr-1) and winter (on
average 0.39 ppb yr-1) could be due to increasing European
background ozone levels, in agreement with other studies. The
statistical model was also able to explain the very high ozone
concentrations in summer 2003, the warmest summer in Switzerland
for at least ~150 years. On average, the measured daily
ozone maximum was 15 ppb (nearly 29%) higher than in the
reference period summer 1992–2002, corresponding to an excess of
5 standard deviations of the summer means of daily ozone maxima in
that period. |
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