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Pressure broadening in the 2ν3 band of methane and its implication on atmospheric retrievals

Frankenberg, Christian; Warneke, Thorsten; Butz, André; Aben, Ilse; Hase, Frank 1; Spietz, Peter; Brown, Linda R.
1 Institut für Meteorologie und Klimaforschung (IMK), Karlsruher Institut für Technologie (KIT)


N2-broadened half widths and pressure shifts were obtained for transitions in the 2ν3 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 N2 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. ... mehr

Verlagsausgabe §
DOI: 10.5445/IR/1000068504
DOI: 10.5194/acp-8-5061-2008
Zitationen: 83
Zitationen: 104
Cover der Publikation
Zugehörige Institution(en) am KIT Institut für Meteorologie und Klimaforschung – Atmosphärische Spurenstoffe und Fernerkundung (IMK-ASF)
Publikationstyp Zeitschriftenaufsatz
Publikationsjahr 2008
Sprache Englisch
Identifikator ISSN: 1680-7324, 1680-7316
KITopen-ID: 1000068504
HGF-Programm 12.03.01 (POF I, LK 01) Zeitliche Variation und Trends
Erschienen in Atmospheric chemistry and physics
Verlag European Geosciences Union (EGU)
Band 8
Heft 17
Seiten 5061–5075
Nachgewiesen in Web of Science
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