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Titel |
Extension of the long-term total column time series of atmospheric methane above the Jungfraujoch station: analysis of grating infrared spectra between 1976 and 1989 |
VerfasserIn |
Whitney Bader, Bernard Lejeune, Philippe Demoulin, Pierre Duchatelet, Ginette Roland, Kengo Sudo, Hisashi Yashiro, Emmanuel Mahieu |
Konferenz |
EGU General Assembly 2011
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 13 (2011) |
Datensatznummer |
250048458
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Zusammenfassung |
Methane (CH4) is one of the most abundant greenhouse gases in the Earth’s atmosphere, with
current mean volume mixing ratio close to 1800 ppb. Since methane has a global warming
potential of 25 (100-yr horizon) and an atmospheric lifetime of 12 years, the Kyoto
Protocol has included it among the species to be regulated to limit global warming.
Anthropogenic sources of methane are mainly energy production (coal and leaks) and
agriculture while main natural sources are swamps and biomass waste. The main sink of
methane is oxidation in the troposphere, primarily by reaction with the hydroxyl
radical.
Methane trends have exhibited significant changes during the last twenty-five years. For
instance, long-term monitoring of its vertical total column above the high-altitude station of
the Jungfraujoch (46.5Ë N, 8Ë E, 3580 m asl) has indeed allowed to derive column changes
ranging from +0.72% in 1987-1988 to +0.14% in 1999-2000 (Zander et al., 2002), relative to
1988 and 2000, respectively. More recently and for the same site, Duchatelet et al. (2010)
have even reported a significant slowdown of -0.02%/yr between years 2000 and 2005.
This study also showed that since then, CH4 is on the rise again, at a rate close to
+0.30%/yr.
While the numbers reported here above have been derived from the Fourier Transform
Infrared (FTIR) data set starting in 1984, earlier pioneering observations have been collected
at the Jungfraujoch since 1950, using grating spectrometers. During the 1958-1975 period,
the main objectives has been the study of the solar photosphere in the visible and the near
infrared and the publication of high-resolution solar atlases. From 1976 to 1989, narrow-band
IR solar absorption observations achieving a spectral resolution of about 0.02 cm-1 have
been recorded with the high-performance double-pass grating spectrometer. Analysis of these
historical spectra provides a unique opportunity to extend the Jungfraujoch’s total
column time series of important atmospheric gases, including methane, by nearly 10
years.
The aim of this contribution is to present the inversion strategy adopted to derive CH4
from the grating spectra, using the SFIT-2 algorithm (v3.91) We will evaluate the
impact of resolution, spectroscopic parameters (from the EU HYMN project -see
www.knmi.nl/samen/hymn-, and from HITRAN 2004), atmospheric pressure and
temperature profiles on the error budget. The 1976-1989 total column time series produced
will be presented and critically discussed. In particular, we will identify and correct for
possible biases between double-pass grating spectrometer measurements and more recent
FTIR total columns. The harmonized and consolidated time series will be investigated to
characterize the long-term trend of methane for the 1976-2010 time period. Comparisons
with synthetic data produced by the CHASER 3-dimensional chemical transport model will
also be presented and analyzed.
Acknowledgments
The University of Liège contribution to the present work has primarily been
supported by the SSD program (AGACC-I and –II projects) funded by the Belgian
Federal Science Policy Office, Brussels and by the Swiss GAW-CH program. We
thank the International Foundation High Altitude Research Stations Jungfraujoch
and Gornergrat (HFSJG, Bern) for supporting the facilities needed to perform the
observations.
References
Duchatelet, P., E. Mahieu, R. Zander, and R. Sussmann, Trends of CO2, CH4 and N2O
over 1985-2010 from high-resolution FTIR solar observations at the Jungfraujoch station,
Geophysical Research Abstracts, Vol. 12, EGU2010-15418-2, 2010.
Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J.
Lean, D.C. Lowe, G. Myhre, J. Nganga, R. Prinn, G. Raga, M. Schulz and R. Van Dorland,
2007: Changes in Atmospheric Constituents and in Radiative Forcing. In: Climate Change
2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment
Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M.
Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller (eds.)].
Cambridge University Press, Cambridge, United Kingdom and New York, NY,
USA.
Zander, R., E. Mahieu, C. Servais, et al., Potential of the NDSC in support of the Kyoto
Protocol : Examples from the station Jungfraujoch, Switzerland, in Non-CO2 Greenhouse
Gases (NCGG-3): Scientific Understanding, Control Options, and policy Aspects, Proc. 3rd
International Symp., Maastricht, The Netherlands, 21-23 January 2002, edited by J. van Ham,
A.P.M. Baede, R. Guicheret, and J. Williams-Jacobse, 305-310, Millpress, Rotterdam, The
Netherlands, 2002. |
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