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12 May 2012
Article (Scientific journals)
Decrease of the Carbon Tetrachloride (CCl4) Loading above Jungfraujoch, based on High Resolution Infrared Solar Spectra recorded between 1999 and 2011
Rinsland, C. P.; Mahieu, Emmanuel  ; Demoulin, Philippe  et al.
2012 • In Journal of Quantitative Spectroscopy and Radiative Transfer, 113, p. 1322-1329
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Keywords :
carbon tetrachloride; atmospheric composition and trends; FTIR spectroscopy; Jungfraujoch station; NDACC; Montreal Protocol; Kyoto Protocol
Abstract :
[en] The long-term trend of the atmospheric carbon tetrachloride (CCl4) burden has been retrieved from high spectral resolution infrared solar absorption spectra recorded between January 1999 and June 2011. The observations were made with a Fourier transform spectrometer at the northern mid-latitude, high altitude Jungfraujoch station in Switzerland (46.5°N latitude, 8.0°E longitude, 3580 m altitude). Total columns were derived from spectrometric analysis of the strong CCl4 ν3 band at 794 cm-1, accounting for all interfering molecules (e.g., H2O, CO2, O3, and a dozen weakly absorbing gases). A significant improvement in the fitting residuals and in the retrieved CCl4 columns was obtained by taking into account line mixing in a strong interfering CO2 Q branch. This procedure had never been implemented in remote sensing CCl4 retrievals though its importance was noted in earlier studies. A fit to the CCl4 daily mean total column time series returns a statistically-significant long-term trend of (-1.49±0.08 x 1013 molec./cm2)/yr, 2-σ. This corresponds to an annual decrease of (-1.31±0.07) pptv for the mean free tropospheric volume mixing ratio. Furthermore, the total column data set reveals a weak seasonal cycle with a peak-to-peak amplitude of 4.5 %, with minimum and maximum values occurring in mid-February and mid-September, respectively. This small seasonal modulation is attributed primarily to the residual influence of tropopause height changes throughout the year. The negative trend of the CCl4 loading reflects the continued impact of the regulations implemented by the Montreal Protocol and its strengthening amendments and adjustments. Despite this statistically significant decrease, the CCl4 molecule currently remains an important contributor to the atmospheric chlorine budget, and thus deserves further monitoring, to ensure continued compliance with these strengthenings, globally. Our present findings are briefly discussed with respect to recent relevant CCl4 investigations at the ground and from space.
Disciplines :
Earth sciences & physical geography
Author, co-author :
Rinsland, C. P.
Mahieu, Emmanuel  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Groupe infra-rouge de phys. atmosph. et solaire (GIRPAS)
Demoulin, Philippe ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Groupe infra-rouge de phys. atmosph. et solaire (GIRPAS)
Zander, Rodolphe ;  Université de Liège - ULiège > Services généraux (Faculté des sciences) > Relations académiques et scientifiques (Sciences)
Servais, Christian ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Groupe infra-rouge de phys. atmosph. et solaire (GIRPAS)
Hartmann, J.-M.
Language :
English
Title :
Decrease of the Carbon Tetrachloride (CCl4) Loading above Jungfraujoch, based on High Resolution Infrared Solar Spectra recorded between 1999 and 2011
Publication date :
2012
Journal title :
Journal of Quantitative Spectroscopy and Radiative Transfer
Publisher :
Pergamon Press - An Imprint of Elsevier Science, Oxford, United Kingdom
Volume :
113
Pages :
1322-1329
Peer reviewed :
Peer Reviewed verified by ORBi

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