Carbon monoxide, methane and carbon dioxide columns retrieved from SCIAMACHY by WFM-DOAS: year 2003 initial data set

摘要

The near-infrarednadir spectra measured bySCIAMACHY on-boardENVISAT contain information onthe vertical columns of important atmospheric tracegases such ascarbon monoxide (CO), methane (CH₄),and carbon dioxide (CO₂).The scientific algorithmWFM-DOAS has been used to retrievethis information.ForCH₄ and CO₂ also column averaged mixing ratios(XCH₄ and XCO₂) have been determinedby simultaneous measurements of the dry air mass.All availablespectra of the year 2003have been processed.We describe the algorithm versions used togenerate the data (v0.4; for methanealso v0.41) and show comparisons of monthly averaged dataover land with global measurements (CO from MOPITT)and models (for CH₄ and CO₂).We show that elevated concentrations of CO resulting from biomass burninghave been detected in reasonable agreement withMOPITT. The measured XCH₄ is enhanced overIndia, south-east Asia, andcentral Africa in September/October 2003 in line with modelsimulations, where they result from surface sources ofmethane such as rice fields and wetlands.The CO₂ measurements over the Northern Hemisphere show the lowestmixing ratios around July in qualitative agreement with model simulationsindicating that the large scale pattern of CO₂ uptakeby the growing vegetation can be detected with SCIAMACHY.We also identified potential problems such as a too low inter-hemisphericgradient for CO, a time dependent bias of the methanecolumns on the order of a few percent,and a few percent too high CO₂ over parts of the Sahara.