CARBON MONOXIDE, METHANE AND CARBON DIOXIDE OVER CHINA RETRIEVED FROM SCIAMACHY/ENVISAT BY WFM-DOAS

The three “carbon gases” carbon monoxide (CO), methane (CH4) and carbon dioxide (CO2) are important atmospheric constituents affecting air quality and climate. We present maps of time averaged (yearly, tri-monthly) CO, CH4 and CO2 over China for the year 2003. They are derived from the near-infrared nadir observations of the SCIAMACHY spectrometer aboard the European environmental satellite ENVISAT using the scientific WFM-DOAS retrieval algorithm (version 0.4 for CO2; version 0.5 for CO and CH4). The maps show vertical columns of carbon monoxide and dry-air column averaged mixing ratios of methane (denoted XCH4) and CO2 (XCO2). The SCIAMACHY near-infrared nadir observations are nearly equally sensitive to concentration changes at all altitude levels including the boundary layer and therefore enable the detection of surface source regions of carbon monoxide, methane, and CO2. The measurement errors for CO and methane are small enough to clearly identify at least moderate to strong source regions. The XCO2 measurements are more difficult to interpret because the measurement error due to, e.g., aerosol and albedo variability, is currently on the order of the weak source/sink signal to be detected. Our future work will aim at reducing the sensitivity to these and other error sources.