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| Titel |
Analysis of stratospheric NO2 trends above Jungfraujoch using ground-based UV-visible, FTIR, and satellite nadir observations |
| VerfasserIn |
F. Hendrick, E. Mahieu, G. E. Bodeker, K. F. Boersma, M. P. Chipperfield, M. Mazière, I. Smedt, P. Demoulin, C. Fayt, C. Hermans, K. Kreher, B. Lejeune, G. Pinardi, C. Servais, R. Stübi, R. der A., J.-P. Vernier, M. Roozendael |
| 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 (2012-09-28), S.8851-8864 |
| Datensatznummer |
250011482
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| Publikation (Nr.) |
 copernicus.org/acp-12-8851-2012.pdf |
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| Zusammenfassung |
| The trend in stratospheric NO2 column at the NDACC (Network for the
Detection of Atmospheric Composition Change) station of Jungfraujoch
(46.5° N, 8.0° E) is assessed using ground-based FTIR and
zenith-scattered visible sunlight SAOZ measurements over the period 1990 to
2009 as well as a composite satellite nadir data set constructed from
ERS-2/GOME, ENVISAT/SCIAMACHY, and METOP-A/GOME-2 observations over the
1996–2009 period. To calculate the trends, a linear least squares regression
model including explanatory variables for a linear trend, the mean annual
cycle, the quasi-biennial oscillation (QBO), solar activity, and
stratospheric aerosol loading is used. For the 1990–2009 period,
statistically indistinguishable trends of
−3.7 ± 1.1% decade−1 and
−3.6 ± 0.9% decade−1 are derived for the SAOZ and FTIR
NO2 column time series, respectively. SAOZ, FTIR, and satellite nadir data
sets show a similar decrease over the 1996–2009 period, with trends of
−2.4 ± 1.1% decade−1, −4.3 ± 1.4% decade−1, and
−3.6 ± 2.2% decade−1, respectively. The fact that these declines are
opposite in sign to the globally observed +2.5% decade−1 trend in N2O,
suggests that factors other than N2O are driving the evolution of
stratospheric NO2 at northern mid-latitudes. Possible causes of the
decrease in stratospheric NO2 columns have been investigated. The most
likely cause is a change in the NO2/NO partitioning in favor of NO, due to
a possible stratospheric cooling and a decrease in stratospheric chlorine
content, the latter being further confirmed by the negative trend in the
ClONO2 column derived from FTIR observations at Jungfraujoch.
Decreasing ClO concentrations slows the NO + ClO → NO2 + Cl
reaction and a stratospheric cooling slows the
NO + O3 → NO2 + O2 reaction, leaving more NOx
in the form of NO. The slightly positive trends in ozone estimated from
ground- and satellite-based data sets are also consistent with the decrease
of NO2 through the NO2 + O3 → NO3 + O2
reaction. Finally, we cannot rule out the possibility that a strengthening of
the Dobson-Brewer circulation, which reduces the time available for N2O
photolysis in the stratosphere, could also contribute to the observed decline
in stratospheric NO2 above Jungfraujoch. |
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