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| Titel |
Increasing ozone in marine boundary layer inflow at the west coasts of North America and Europe |
| VerfasserIn |
D. D. Parrish, D. B. Millet, A. H. Goldstein |
| 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 ; 9, no. 4 ; Nr. 9, no. 4 (2009-02-19), S.1303-1323 |
| Datensatznummer |
250006928
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| Publikation (Nr.) |
 copernicus.org/acp-9-1303-2009.pdf |
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| Zusammenfassung |
| An effective method is presented for determining the ozone (O3) mixing
ratio in the onshore flow of marine air at the North American west coast. By
combining the data available from all marine boundary layer (MBL) sites with
simultaneous wind data, decadal temporal trends of MBL O3 in all
seasons are established with high precision. The average springtime temporal
trend over the past two decades is 0.46 ppbv/yr with a 95% confidence
limit of 0.13 ppbv/yr, and statistically significant trends are found for
all seasons except autumn, which does have a significantly smaller trend
than other seasons. The average trend in mean annual ozone is 0.34±0.09 ppbv/yr.
These decadal trends at the North American west coast present
a striking comparison and contrast with the trends reported for the European
west coast at Mace Head, Ireland. The trends in the winter, spring and
summer seasons compare well at the two locations, while the Mace Head trend
is significantly greater in autumn. Even though the trends are similar, the
absolute O3 mixing ratios differ markedly, with the marine air arriving
at Europe in all seasons containing 7±2 ppbv higher ozone than marine
air arriving at North America. Further, the ozone mixing ratios at the North
American west coast show no indication of stabilizing as has been reported
for Mace Head. In a larger historical context the background boundary layer
O3 mixing ratios over the 130 years covered by available data have
increased substantially (by a factor of two to three), and this increase
continues at present, at least in the MBL of the Pacific coast region of
North America. The reproduction of the increasing trends in MBL O3 over
the past two decades, as well as the difference in the O3 mixing ratios
between the two coastal regions will present a significant challenge for
global chemical transport models. Further, the ability of the models to at
least semi-quantitatively reproduce the longer-term, historical trends may
an even greater challenge. |
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