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| Titel |
Have primary emission reduction measures reduced ozone across Europe? An analysis of European rural background ozone trends 1996–2005 |
| VerfasserIn |
R. C. Wilson, Z. L. Fleming, P. S. Monks, G. Clain, S. Henne, I. B. Konovalov, S. Szopa, L. Menut |
| 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. 1 ; Nr. 12, no. 1 (2012-01-09), S.437-454 |
| Datensatznummer |
250010444
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| Publikation (Nr.) |
 copernicus.org/acp-12-437-2012.pdf |
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| Zusammenfassung |
National and European legislation over the past 20 yr, and the modernisation
or removal of industrial sources, have significantly reduced European ozone
precursor emissions. This study quantifies observed and modelled European
ozone annual and seasonal linear trends from 158 harmonised rural background
monitoring stations over a constant time period of a decade (1996–2005).
Mean ozone concentrations are investigated, in addition to the ozone 5th
percentiles as a measure of the baseline or background conditions, and the
95th percentiles that are representative of the peak concentration levels.
This study aims to characterise and quantify surface European ozone
concentrations and trends and assess the impact of the changing anthropogenic
emission tracers on the observed and modelled trends.
Significant (p<0.1) positive annual trends in ozone mean, 5th and 95th
percentiles are observed at 54 %, 52 % and 45 % of sites respectively
(85 sites, 82 sites and 71 sites). Spatially, sites in central and
north-western Europe tend to display positive annual ozone trends in mean,
5th and 95th percentiles. Significant negative annual trends in ozone mean
5th and 95th percentiles are observed at 11 %, 12 % and 12 % of sites
respectively (18 sites, 19 sites and 19 sites) which tend to be located in
the eastern and south-western extremities of Europe. European-averaged annual
trends have been calculated from the 158 sites in this study. Overall there
is a net positive annual trend in observed ozone mean
(0.16±0.02 ppbv yr−1 (2σ error)), 5th
(0.13±0.02 ppbv yr−1) and 95th
(0.16±0.03 ppbv yr−1) percentiles, representative of positive
trends in mean, baseline and peak ozone. Assessing the sensitivity of the
derived overall trends to the constituent years shows that the European
heatwave year of 2003 has significant positive influence and 1998 the
converse effect; demonstrating the masking effect of inter-annual variability
on decadal based ozone trends.
The European scale 3-D CTM CHIMERE was used to simulate hourly O3
concentrations for the period 1996–2005. Comparisons between the 158
observed ozone trends to those equivalent sites extracted from regional
simulations by CHIMERE better match the observed increasing annual ozone
(predominantly in central and north-western Europe) for 5th percentiles, than
for mean or 95th ozone percentiles. The European-averaged annual ozone trend
in CHIMERE 5th percentiles (0.13±0.01 ppbv yr−1) matches the
corresponding observed trend extremely well, but displays a negative trend
for the 95th percentile (−0.03±0.02 ppbv yr−1) where a
positive ozone trend is observed. Inspection of the EU-averaged monthly means
of ozone shows that the CHIMERE model is overestimating the summer month
O3 levels.
In comparison to trends in EMEP emissions inventories, with the exception of
Austria-Hungary, we do not find that anthropogenic NOx and VOC
reductions have a substantial effect on observed annual mean O3
trends in the rest of Europe. On a ten year time-scale presented in this
study, O3 trends related to anthropogenic NOx and VOC
reductions are being masked as a result of a number of factors including
meteorological variability, changes in background ozone and shifts in source
patterns. |
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