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| Titel |
First retrievals of HCFC-142b from ground-based high-resolution FTIR solar observations: application to high-altitude Jungfraujoch spectra |
| VerfasserIn |
Emmanuel Mahieu, Simon O'Doherty, Stefan Reimann, Martin Vollmer, Whitney Bader, Benoît Bovy, Bernard Lejeune, Philippe Demoulin, Ginette Roland, Christian Servais, Rodolphe Zander |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250072633
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| Zusammenfassung |
| Hydrofluorocarbons (HCFCs) are the first substitutes to the long-lived ozone depleting
halocarbons, in particular the chlorofluorocarbons (CFCs). Given the complete ban of the
CFCs by the Montreal Protocol, its Amendments and Adjustments, HCFCs are on the rise,
with current rates of increase substantially larger than at the beginning of the 21st century.
HCFC-142b (CH3CClF2) is presently the second most abundant HCFCs, after HCFC-22
(CHClF2). It is used in a wide range of applications, including as a blowing foam agent, in
refrigeration and air-conditioning. Its concentration will soon reach 25 ppt in the northern
hemisphere, with mixing ratios increasing at about 1.1 ppt/yr [Montzka et al., 2011]. The
HCFC-142b lifetime is estimated at 18 years. With a global warming potential of 2310
on a 100-yr horizon, this species is also a potent greenhouse gas [Forster et al.,
2007].
First space-based retrievals of HCFC-142b have been reported by Dufour et al. [2005]. 17
occultations recorded in 2004 by the Canadian ACE-FTS instrument (Atmospheric
Chemistry Experiment – Fourier Transform Spectrometer, onboard SCISAT-1) were
analyzed, using two microwindows (1132.5–1135.5 and 1191.5–1195.5 cm-1). In 2009,
Rinsland et al. determined the HCFC-142b trend near the tropopause, from the analysis of
ACE-FTS observations recorded over the 2004–2008 time period. The spectral region used in
this study extended from 903 to 905.5 cm-1.
In this contribution, we will present the first HCFC-142b measurements from
ground-based high-resolution Fourier Transform Infrared (FTIR) solar spectra. We use
observations recorded at the high altitude station of the Jungfraujoch (46.5°N, 8°E, 3580 m
asl), with a Bruker 120HR instrument, in the framework of the Network for the Detection of
Atmospheric Composition Change (NDACC, visit http://www.ndacc.org). The retrieval of
HCFC-142b is very challenging, with simulations indicating only weak absorptions, lower
than 1% for low sun spectra and current concentrations. Among the four microwindows
tested, the region extending from 900 to 906 cm-1 proved to be the most appropriate, with
limited interferences, in particular from water vapor. A total column time series spanning the
2004-2012 time period will be presented, analyzed and critically discussed. After
conversion of our total columns to concentrations, we will compare our results
with in situ measurements performed in the northern hemisphere by the AGAGE
network.
Acknowledgments
The University of Liège contribution to the present work has primarily been supported by
the SSD and PRODEX programs (AGACC-II and A3C projects, respectively) funded by the
Belgian Federal Science Policy Office (BELSPO), Brussels. E. Mahieu is Research
Associate with the F.R.S. – FNRS. Laboratory developments and mission expenses at
the Jungfraujoch station were funded by the F.R.S. – FNRS and the Fédération
Wallonie-Bruxelles, respectively. We thank the International Foundation High Altitude
Research Stations Jungfraujoch and Gornergrat (HFSJG, Bern) for supporting the facilities
needed to perform the observations. We further acknowledge the vital contribution
from all the Belgian colleagues in performing the Jungfraujoch observations used
here.
References
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HCFC-142b from space using ACE-FTS infrared spectra, Geophys. Res. Lett., 32, L15S09,
doi:10.1029/2005GL022422, 2005.
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