Atmospheric methane and carbon dioxide from SCIAMACHY satellite data: initial comparison with chemistry and transport models

Abstract

Abstract. The remote sensing of the atmospheric greenhouse gases methane (CH 4 ) and carbon dioxide (CO 2 ) in the troposphere from instrumentation aboard satellites is a new area of research. In this manuscript, results obtained from observations of the up-welling radiation in the near-infrared by SCIAMACHY on board ENVISAT are presented. Vertical columns of CH 4 , CO 2 and oxygen (O 2 ) have been retrieved and the (air or) O 2 -normalised CH 4 and CO 2 column amounts, the dry air column averaged mixing ratios XCH 4 and XCO 2 derived. In this manuscript the first results, obtained by using the version 0.4 of the Weighting Function Modified (WFM) DOAS retrieval algorithm applied to SCIAMACHY data, are described and compared with global models. For the set of individual cloud free measurements over land the standard deviation of the difference with respect to the models is in the range ∼100-200 ppbv (5-10%) for XCH 4 and ∼14-32 ppmv (4-9%) for XCO 2 . The interhemispheric difference of the methane mixing ratio, as determined from single day data, is in the range 30-110 ppbv and in reasonable agreement with the corresponding model data (48-71 ppbv). The weak inter-hemispheric difference of the CO 2 mixing ratio can also be detected with single day data. The spatiotemporal pattern of the measured and the modelled XCO 2 are in reasonable agreement. However, the amplitude of the difference between the maximum and the minimum for SCIAMACHY XCO 2 is about ±20 ppmv which is about a factor of four larger than the variability of the model data which is about ±5 ppmv. More studies are needed to explain the observed differences. The XCO 2 model field shows low CO 2 concentrations beginning of January 2003 over a spatially extended CO 2 sink region located Correspondence to: M. Buchwitz (michael.buchwitz@iup.physik.uni-bremen.de) in southern tropical/sub-tropical Africa. The SCIAMACHY data also show low CO 2 mixing ratios over this area. According to the model the sink region becomes a source region about six months later and exhibits higher mixing ratios. The SCIAMACHY and the model data over this region show a similar time dependence over the period from January to October 2003. These results indicate that for the first time a regional CO 2 surface source/sink region has been detected by measurements from space. The interpretation of the SCIAMACHY CO 2 and CH 4 measurements is difficult, e.g., because the error analysis of the currently implemented retrieval algorithm indicates that the retrieval errors are on the same order as the small greenhouse gas mixing ratio changes that are to be detected.

The global methane budget 2000–2012

“…The combined datasets provide the longest time series of globally averaged CH 4 abundance. Since the early 2000s, remotely sensed retrievals of CH 4 have provided CH 4 atmospheric columnaveraged mole fractions (Buchwitz et al, 2005a;Frankenberg et al, 2005;Butz et al, 2011;Crevoisier et al, 2009;. Fourier transform infrared (FTIR) measurements at fixed locations also provide methane column observations .…”

“…The atmospheric observation density has improved in the tropics with satellite-based column-averaged methane mixing ratios (Buchwitz et al, 2005b;Frankenberg et al, 2005;Butz et al, 2011). However, the optimal usage of satellite data remains limited by systematic errors in satellite retrievals (Bergamaschi et al, 2009;Locatelli et al, 2015).…”

Algorithm update of the GOSAT/TANSO-FTS thermal infrared CO<sub>2</sub> product (version 1) and validation of the UTLS CO<sub>2</sub> data using CONTRAIL measurements

“…The Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) on the Environmental Satellite (EN-VISAT) first observed CO 2 column-averaged dry-air mole fractions (XCO 2 ) from spectra at 1.57 µm (Buchwitz et al, 2005;Barkley et al, 2006). The Thermal and Near Infrared Sensor for Carbon Observation (TANSO)-Fourier Transform Spectrometer (FTS) on board the Greenhouse Gases Observing Satellite (GOSAT), which was launched in 2009 (Yokota et al, 2009), has observed XCO 2 with high precision by utilizing the 1.6 and/or 2.0 µm CO 2 absorption bands (Yoshida et al, 2011O'Dell et al, 2012;Butz et al, 2011;Cogan et al, 2012).…”

Characterization of Tropospheric Emission Spectrometer (TES) CO<sub>2</sub> for carbon cycle science

“…SCIAMACHY was launched on the Envisat platform in 2001 and measures reflected sunlight at UV-SWIR wavelengths, with peak sensitivity near the surface. Buchwitz et al (2005Buchwitz et al ( , 2007, Bösch et al (2006) and Barkley et al (2006) have presented daytime CO 2 retrievals over land from SCIAMACHY data. AIRS was launched on the EOS-Aqua platform in 2002 and different techniques have been used to retrieve atmospheric CO 2 abundances from AIRS radiances.…”