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| Titel |
Observed and simulated time evolution of HCl, ClONO2, and HF total column abundances |
| VerfasserIn |
R. Kohlhepp, R. Ruhnke, M. P. Chipperfield, M. Mazière, J. Notholt, S. Barthlott, R. L. Batchelor, R. D. Blatherwick, Th. Blumenstock, M. T. Coffey, P. Demoulin, H. Fast, W. Feng, A. Goldman, D. W. T. Griffith, K. Hamann, J. W. Hannigan, F. Hase, N. B. Jones, A. Kagawa, I. Kaiser, Y. Kasai, O. Kirner, W. Kouker, R. Lindenmaier, E. Mahieu, R. L. Mittermeier, B. Monge-Sanz, I. Morino, I. Murata, H. Nakajima, M. Palm, C. Paton-Walsh, U. Raffalski, Th. Reddmann, M. Rettinger, C. P. Rinsland, E. Rozanov, M. Schneider, C. Senten, C. Servais, B.-M. Sinnhuber, D. Smale, K. Strong, R. Sussmann, J. R. Taylor, G. Vanhaelewyn, T. Warneke, C. Whaley, M. Wiehle, S. W. Wood |
| 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. 7 ; Nr. 12, no. 7 (2012-04-12), S.3527-3556 |
| Datensatznummer |
250011026
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| Publikation (Nr.) |
 copernicus.org/acp-12-3527-2012.pdf |
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| Zusammenfassung |
Time series of total column abundances of hydrogen chloride (HCl), chlorine
nitrate (ClONO2), and hydrogen fluoride (HF) were determined from
ground-based Fourier transform infrared (FTIR) spectra recorded at 17 sites
belonging to the Network for the Detection of Atmospheric Composition Change
(NDACC) and located between 80.05° N and 77.82° S. By
providing such a near-global overview on ground-based measurements of the two
major stratospheric chlorine reservoir species, HCl and ClONO2, the
present study is able to confirm the decrease of the atmospheric inorganic
chlorine abundance during the last few years. This decrease is expected
following the 1987 Montreal Protocol and its amendments and adjustments,
where restrictions and a subsequent phase-out of the prominent anthropogenic
chlorine source gases (solvents, chlorofluorocarbons) were agreed upon to
enable a stabilisation and recovery of the stratospheric ozone layer. The
atmospheric fluorine content is expected to be influenced by the Montreal
Protocol, too, because most of the banned anthropogenic gases also represent
important fluorine sources. But many of the substitutes to the banned gases
also contain fluorine so that the HF total column abundance is expected to
have continued to increase during the last few years.
The measurements are compared with calculations from five different models:
the two-dimensional Bremen model, the two chemistry-transport models KASIMA
and SLIMCAT, and the two chemistry-climate models EMAC and SOCOL. Thereby,
the ability of the models to reproduce the absolute total column amounts, the
seasonal cycles, and the temporal evolution found in the FTIR measurements is
investigated and inter-compared. This is especially interesting because the
models have different architectures. The overall agreement between the
measurements and models for the total column abundances and the seasonal
cycles is good.
Linear trends of HCl, ClONO2, and HF are calculated from both measurement
and model time series data, with a focus on the time range 2000–2009. This
period is chosen because from most of the measurement sites taking part in
this study, data are available during these years. The precision of the
trends is estimated with the bootstrap resampling method. The sensitivity of
the trend results with respect to the fitting function, the time of year
chosen and time series length is investigated, as well as a bias due to the
irregular sampling of the measurements.
The measurements and model results investigated here agree qualitatively on a
decrease of the chlorine species by around 1% yr−1. The models simulate an
increase of HF of around 1% yr−1. This also agrees well with most of the
measurements, but some of the FTIR series in the Northern Hemisphere show a
stabilisation or even a decrease in the last few years. In general, for all
three gases, the measured trends vary more strongly with latitude and
hemisphere than the modelled trends. Relative to the FTIR measurements, the
models tend to underestimate the decreasing chlorine trends and to
overestimate the fluorine increase in the Northern Hemisphere.
At most sites, the models simulate a stronger decrease of ClONO2 than of
HCl. In the FTIR measurements, this difference between the trends of HCl and
ClONO2 depends strongly on latitude, especially in the Northern
Hemisphere. |
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