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| Titel |
On the changing seasonal cycles and trends of ozone at Mace Head, Ireland |
| VerfasserIn |
D. C. Carslaw |
| 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. 12 ; Nr. 5, no. 12 (2005-12-20), S.3441-3450 |
| Datensatznummer |
250003205
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| Publikation (Nr.) |
 copernicus.org/acp-5-3441-2005.pdf |
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| Zusammenfassung |
| A seasonal-trend decomposition technique based on a locally-weighted
regression smoothing (Loess) approach has been used to decompose monthly
ozone concentrations at Mace Head (Ireland) into trend, seasonal and
irregular components. The trend component shows a steady increase from
1990–2004, which is confirmed by statistical testing which shows that ozone
concentrations at Mace Head have increased at the p=0.06 level by
0.18±0.04 ppb yr−1. By considering different air mass origins using
a trajectory analysis, it has been possible to separate air masses into
"polluted" and "unpolluted" origins. The seasonal-trend decomposition
technique confirms the different seasonal cycles of these air mass origins
with unpolluted air mass maxima in April and polluted air mass maxima in
July/August. A detailed consideration of the seasonal component reveals
different behaviour depending on the air mass origin. For baseline
unpolluted air arriving at Mace Head there has been a gradual increase in
the seasonal amplitude, driven by a declining summertime component. The
amplitude of the seasonal component of baseline air is controlled by a
maximum in April and a minimum in July. For polluted air mass trajectories,
there was a substantial reduction in the amplitude of the seasonal component
from 1990–1997. However, post-1997 results indicate that the seasonal
amplitude in polluted air masses arriving at Mace Head is increasing.
Furthermore, there has been a shift in the months controlling the size of
the seasonal amplitude in polluted air from a maximum in May and minimum in
January in 1990 to a maximum in April and a minimum in July by 2001. This
finding suggests that there has been a steadily decreasing influence of
polluted air masses arriving from Europe. These air masses have therefore
increasingly taken on the attributes of baseline air. |
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