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| Titel |
Trends of HCl, ClONO2, and HF column abundances from ground-based FTIR measurements in Kiruna (Sweden) in comparison with KASIMA model calculations |
| VerfasserIn |
R. Kohlhepp, S. Barthlott, T. Blumenstock, F. Hase, I. Kaiser, U. Raffalski, R. Ruhnke |
| 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 ; 11, no. 10 ; Nr. 11, no. 10 (2011-05-18), S.4669-4677 |
| Datensatznummer |
250009746
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| Publikation (Nr.) |
 copernicus.org/acp-11-4669-2011.pdf |
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| Zusammenfassung |
Trends of hydrogen chloride (HCl), chlorine nitrate (ClONO2), and hydrogen
fluoride (HF) total column abundances above Kiruna (Northern Sweden,
67.84° N, 20.41° E) derived from nearly 14 years (1996–2009)
of measurement and model data are presented. The measurements have been
performed with a Bruker 120 HR (later Bruker 125 HR) Fourier transform
infrared (FTIR) spectrometer and the chemistry-transport model (CTM) used was
KASIMA (KArlsruhe SImulation model of the Middle Atmosphere). The total
column abundances of ClONO2 and HF calculated by KASIMA agree quite well
with the FTIR measurements while KASIMA tends to underestimate the HCl
columns.
To calculate the long-term trends, a linear function combined with an annual
cycle was fitted to the data using a least squares method. The precision of
the resulting trends was estimated with the bootstrap resampling method.
For HF, both model and measurements show a positive trend that seems to
decrease in the last few years. This suggests a stabilisation of the HF total
column abundance. Between 1996 and 2009, KASIMA simulates an increase of
(+1.51±0.07) %/yr which exceeds the FTIR result of
(+0.65±0.25) %/yr.
The trends determined for HCl and ClONO2 are significantly negative over
the time period considered here. This is expected because the emission of
their precursors (chlorofluorocarbons and hydrochlorofluorocarbons) has been
restricted in the Montreal Protocol in 1987 and its amendments and
adjustments. The trend for ClONO2 from the FTIR measurements amounts to
(−3.28±0.56) %/yr and the one for HCl to (−0.81±0.23) %/yr. KASIMA
simulates a weaker decrease: For ClONO2, the result is (−0.90±0.10) %/yr
and for HCl (−0.17±0.06) %/yr. Part of the difference
between measurement and model data can be explained by sampling and the
stronger annual cycle indicated by the measurements. There is a factor of
about four between the trends of HCl and ClONO2 above Kiruna for both
measurement and model data. |
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