HR: 11:15h
AN: A12D-04    [Abstracts]
TI: Satellite Chartography of Atmospheric Methane from SCIAMACHY onboard ENVISAT
AU: * Frankenberg, C
EM: cfranken@iup.uni-heidelberg.de
AF: Institute of Environmental Physics, Heidelberg, INF 229, Heidelberg, 69117 Germany
AU: Meirink, J
EM: meirink@knmi.nl
AF: Royal Netherlands Meteorological Institute (KNMI), P.O. Box 201, De Bilt, 3730 Netherlands
AU: Bergamaschi, P
EM: peter.bergamaschi@jrc.it
AF: Joint Research Centre of the European Commission (EC-JRC) Institute for Environment and Sustainability (IES), TP 263 Via Fermi, Ispra (VA), 21020 Italy
AU: Koerner, S
EM: Stefan.Koerner@bgc-jena.mpg.de
AF: Max Planck Institute for Biogeochemistry, P.O. Box 100164, Jena, 07701 Germany
AU: Heimann, M
EM: martin.heimann@bgc-jena.mpg.de
AF: Max Planck Institute for Biogeochemistry, P.O. Box 100164, Jena, 07701 Germany
AU: Platt, U
EM: Ulrich.Platt@iup.uni-heidelberg.de
AF: Institute of Environmental Physics, Heidelberg, INF 229, Heidelberg, 69117 Germany
AU: Wagner, T
EM: Thomas.Wagner@iup.uni-heidelberg.de
AF: Institute of Environmental Physics, Heidelberg, INF 229, Heidelberg, 69117 Germany
AB: The UV/Vis/near infrared spectrometer SCIAMACHY onboard the European ENVISAT satellite enables total column retrieval of atmospheric methane with high sensitivity to the lower troposphere. We apply an Iterative Maximum A Posteriori DOAS approach to derive vertical column densities of methane and carbon dioxide. Due to the low variability of CO₂, total column retrievals of CO₂ are used as proxy for the probed atmospheric column and thereby allow us to convert methane column densities to column averaged mixing ratios. In addition, CO₂ abundances are modeled to account for possibly large seasonal variations in its total column. The retrievals have been compared with methane abundances derived from the atmospheric transport models TM4 and TM5. High correlations between observed and simulated global CH₄ column averaged mixing ratios are calculated for the entire 2-year period from 2003 through 2004. The theoretical retrieval precision of about 1.8% corresponds well with the observed average standard deviation between observations and simulations, which is on the order of 30 ppb. On the global scale, the most pronounced CH₄ signal arises from source regions over India and South East Asia, broadly consistent with model simulations. SCIAMACHY retrievals, however, indicate higher CH₄ abundances over tropical Africa and tropical America, pointing to hitherto underestimated CH₄ emissions from tropical landmasses. Apart from the presentation of the retrieved methane abundances, we discuss the retrieval algorithm and quantify possible impact factors on precision and accuracy (such as clouds and aerosols).
DE: 0330 Geochemical cycles (1030)
DE: 0365 Troposphere: composition and chemistry
DE: 0933 Remote sensing
DE: 1610 Atmosphere (0315, 0325)
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005