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| Titel |
An approach to retrieve information on the carbonyl fluoride (COF2) vertical distributions above Jungfraujoch by FTIR multi-spectrum multi-window fitting |
| VerfasserIn |
P. Duchatelet, E. Mahieu, R. Ruhnke, W. Feng, M. Chipperfield, P. Demoulin, P. Bernath, C. D. Boone, K. A. Walker, C. Servais, O. Flock |
| 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. 22 ; Nr. 9, no. 22 (2009-11-30), S.9027-9042 |
| Datensatznummer |
250007775
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| Publikation (Nr.) |
 copernicus.org/acp-9-9027-2009.pdf |
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| Zusammenfassung |
| We present an original multi-spectrum fitting procedure to retrieve volume
mixing ratio (VMR) profiles of carbonyl fluoride (COF2) from
ground-based high resolution Fourier transform infrared (FTIR) solar
spectra. The multi-spectrum approach consists of simultaneously combining,
during the retrievals, all spectra recorded consecutively during the same
day and with the same resolution. Solar observations analyzed in this study
with the SFIT-2 v3.91 fitting algorithm correspond to more than 2900 spectra
recorded between January 2000 and December 2007 at high zenith angles, with
a Fourier Transform Spectrometer operated at the high-altitude International
Scientific Station of the Jungfraujoch (ISSJ, 46.5° N latitude, 8.0° E
longitude, 3580 m altitude), Switzerland. The goal of the retrieval strategy
described here is to provide information about the vertical distribution of
carbonyl fluoride. The microwindows used are located in the ν4 or
in the ν4 COF2 infrared (IR) absorption bands. Averaging
kernel and eigenvector analysis indicates that our FTIR retrieval is
sensitive to COF2 inversion between 17 and 30 km, with the major
contribution to the retrieved information always coming from the
measurement. Moreover, there was no significant bias between COF2
partial columns, total columns or VMR profiles retrieved from the two bands.
For each wavenumber region, a complete error budget including all identified
sources has been carefully established. In addition, comparisons of FTIR
COF2 17–30 km partial columns with KASIMA and SLIMCAT 3-D CTMs are also
presented. If we do not notice any significant bias between FTIR and SLIMCAT
time series, KASIMA COF2 17–30 km partial columns are lower of around
25%, probably due to incorrect lower boundary conditions. For each times
series, linear trend estimation for the 2000–2007 time period as well as a
seasonal variation study are also performed and critically discussed. For
FTIR and KASIMA time series, very low COF2 growth rates
(0.4±0.2%/year and 0.3±0.2%/year, respectively) have been derived.
However, the SLIMCAT data set gives a slight negative trend
(−0.5±0.2%/year), probably ascribable to discontinuities in the meteorological
data used by this model. We further demonstrate that all time series are
able to reproduce the COF2 seasonal cycle, which main seasonal
characteristics deduced from each data set agree quite well. |
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