SCIAMACHY/ENVISAT Greenhouse Gas Observations: Methane and Carbon Dioxide over Permafrost Areas
M. Buchwitz, O. Schneising, H. Bovensmann, M. Reuter, and J. P. Burrows
Institute of Environmental Physics (IUP) / Remote Sensing (IFE), University of Bremen FB1, Bremen, Germany
Overview
The spectra of reflected and backscattered solar radiation as measured by SCIAMACHY in nadir observation mode in the near-infrared/short-wave-infrared (NIR/SWIR) spectral region contain information on the vertical columns of the greenhouse gases methane and carbon dioxide. We retrieve this information using a modified DOAS algorithm (WFM-DOAS or WFMD). The latest version is v1.0 [3,5,6]. Our main greenhouse gas data products are dry air column-averaged mole fractions (mixing ratios), denoted XCH4 for methane (in ppb) and XCO2 for CO2 (in ppm), obtained by normalizing the retrieved greenhouse gas columns by corresponding dry air columns. For XCO2 the air columns are obtained using retrieved O2 columns, for XCH4 using retrieved CO2 columns. Until now three years of data have been processed (2003-2005). Here we show some results for 2003 focusing on northern hemispheric mid and high latitudes and comparisons with global model data using TM5 [1,2] for methane and CarbonTracker [4] for carbon dioxide. SCIAMACHY is the first and currently only satellite instrument whose measurements are sensitive to all altitude levels including the boundary layer where the greenhouse gas source/sink signals are largest. The precision/accuracy of the measurements is about 1-2% for methane and about 1-3% for carbon dioxide. Wetlands are a major source of methane (~92-237 Mt/yr). Melting permafrost areas release significant amounts of methane but also carbon dioxide. These two gases are the most important anthropogenic greenhouse gases. It is expected that greenhouse gas emissions from permafrost areas will increase significantly due to global warming. Monitoring of greenhouse gas emissions, e.g. via measured concentrations, and an appropriate understanding of their variable natural and anthropogenic sources and sinks is important in this context but also in the context of the Kyoto protocol.
Methane: Global distributions
http://www.sciencepoles.org/pics/scientific_articles/pe rmafrost_map_or.jpg ACIA (Arctic Climate Impact Assessment), 2004.
Comparison with models
Methane
SCIAMACHY
Carbon dioxide
SCIAMACHY
Methane: Emissions via inverse modelling
First methane emissions via inverse modelling based on the new SCIAMACHY WFMDv1.0 methane data set for 2003 using the TM5 model, a-priori methane emissions, methane surface observations, and a 4D-VAR method to estimate the emissions from the measured concentrations [2]. Courtesy: P. Bergamaschi, EC-JRC, IES, Ispra, Italy
TM5 model
CarbonTracker
Acknowledgements
We thank DLR and ESA for providing us with the SCIAMACHY spectra. This work has been funded by: DLR-Bonn (SADOS and SCIACO2), ESA (GSE PROMOTE), the EC (FP 6 AMFIC), and the State and the University of Bremen. Exchange of information within EC FP 6 Network of Excellence ACCENT is acknowledged. We thank NOAA (P. Tans, W. Peters and colleagues) for providing us with the CarbonTracker CO2 model fields and P. Bergamaschi, EC-JRC, IES, Ispra, Italy, for the TM5 model methane fields.
Selected references
[1] Bergamaschi et al., Satellite chartography of atmospheric methane from SCIAMACHY on board ENVISAT: 2. Evaluation based on inverse model simulations, J. Geophys. Res., 112, 2007. [2] Bergamaschi et al., Estimates of CH4 sources using existing atmospheric inversion models, presentation given at GEMS General Assembly, Exeter, 14-18 January 2008. [3] Buchwitz et al., First direct observation of the atmospheric CO2 year-to-year increase from space, Atmos. Chem. Phys., 2007. [4] Peters et al., An atmospheric perspective on North American carbon dioxide exchange: CarbonTracker, PNAS, 2007. [5] Schneising et al., Three years of greenhouse gas column-averaged dry air mole fractions retrieved from satellite – Part 1: Carbon dioxide, submitted to Atmos. Chem. Phys., 2008. [6] Schneising et al., Three years of greenhouse gas column-averaged dry air mole fractions retrieved from satellite – Part 2: Methane, submitted to Atmos. Chem. Phys., 2008.
www.iup.uni-bremen.de/sciamachy/NIR_NADIR_WFM_DOAS/
Contact: Michael.Buchwitz@iup.physik.uni-bremen.de