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Pressure broadening in the 2v_3 band of methane and its implication on atmospheric retrievals

Frankenberg, C. and Warneke, T. and Butz, A. and Aben, I. and Hase, F. and Spietz, P. and Brown, L. R. (2008) Pressure broadening in the 2v_3 band of methane and its implication on atmospheric retrievals. Atmospheric Chemistry and Physics, 8 (17). pp. 5061-5075. ISSN 1680-7316.

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N_2-broadened half widths and pressure shifts were obtained for transitions in the 2ν_3 methane band. Laboratory measurements recorded at 0.011 cm^(−1) resolution with a Bruker 120 HR Fouriertransform spectrometer were analysed from 5860 to 6185 cm^(−1). A 140 cm gas cell was filled with methane at room temperature and N_2 as foreign gas at pressures ranging from 125 to 900 hPa. A multispectrum nonlinear constrained least squares approach based on Optimal Estimation was applied to derive the spectroscopic parameters by simultaneously fitting laboratory spectra at different ambient pressures assuming a Voigt line-shape. At room temperature, the half widths ranged between 0.030 and 0.071 cm^(−1) atm^(−1), and the pressure shifts varied from –0.002 to –0.025 cm^(−1) atm^(−1) for transitions up to J"=10. Especially for higher rotational levels, we find systematically narrower lines than HITRAN predicts. The Q and R branch of the new set of spectroscopic parameters is further tested with ground based direct sun Fourier transform infrared (FTIR) measurements where systematic fit residuals reduce by about a factor of 3–4. We report the implication of those differences on atmospheric methane measurements using high-resolution ground based FTIR measurements as well as low-resolution spectra from the SCanning Imaging Absorption SpectroMeter for Atmospheric ChartographY (SCIAMACHY) instrument onboard ENVISAT. We find that for SCIAMACHY, a latitudinal and seasonally varying bias of about 1% can be introduced by erroneous broadening parameters.

Item Type:Article
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Frankenberg, C.0000-0002-0546-5857
Warneke, T.0000-0001-5185-3415
Butz, A.0000-0003-0593-1608
Additional Information:© 2008 Author(s). This work is distributed under the Creative Commons Attribution 3.0 License. Received: 26 March 2008. Published in Atmos. Chem. Phys. Discuss.: 29 May 2008. Revised: 4 August 2008. Accepted: 11 August 2008. Published: 1 September 2008. CF is supported by the Dutch science foundation (NWO) through a VENI grant. We acknowledge John Burrows, PI of the SCIAMACHY instrument, for having initiated the SCIAMACHY project. The experimental data for the study of the broadening parameters, used in this study, was recorded in the Molecular Spectroscopy laboratory of the Institute of Environmental Physics and Remote Sensing of the University of Bremen. This laboratory is funded by the University of Bremen and the German Aerospace (DLR) to undertake spectroscopic studies in support of SCIAMACHY science. We thank R. Washenfelder for providing a spectroscopic linelist based on the results of Pine et al. The Netherlands SCIAMACHY Data Center and ESA is greatly acknowledged for providing data and R. van Hees for having written the versatile NADC tools software package. We thank Jan Fokke Merink and Peter Bergamaschi for providing TM5-4DVAR methane model fields and Wouter Peters for providing CarbonTracker results. We also thank A. Segers, C. Schrijvers, and O. Tuinder for providing the ECMWF data. Part of the research described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA). We acknowledge the European Commission for supporting the 6th Framework Programme project HYMN (contract number 037048) and GEOMON (contract number 036677). We further acknowledge exchange of information within the EU 6th FP Network of Excellence ACCENT. Edited by: W. Lahoz
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University of BremenUNSPECIFIED
European Commission 6th Framework Program project HYMN037048
European Commission 6th Framework Program project GEOMON036677
EU 6th FP Network of Excellence ACCENTUNSPECIFIED
Deutsches Zentrum für Luft- und Raumfahrt (DLR)UNSPECIFIED
Issue or Number:17
Record Number:CaltechAUTHORS:20150511-133814600
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Official Citation:Frankenberg, C., Warneke, T., Butz, A., Aben, I., Hase, F., Spietz, P., and Brown, L. R.: Pressure broadening in the 2ν3 band of methane and its implication on atmospheric retrievals, Atmos. Chem. Phys., 8, 5061-5075, doi:10.5194/acp-8-5061-2008, 2008.
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57421
Deposited By: Ruth Sustaita
Deposited On:11 May 2015 21:05
Last Modified:09 Mar 2020 13:19

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