Hamburg 2009 – scientific programme

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UP: Fachverband Umweltphysik

UP 2: Atmosphäre II

UP 2.6: Talk

Tuesday, March 3, 2009, 15:18–15:30, VMP 9 HS

Retrieval of atmospheric CO2 from satellite near-infrared nadir spectra in a scattering atmosphere — •Maximilian Reuter, Michael Buchwitz, Oliver Schneising, Heinrich Bovensmann, and John P. Burrows — Institute of Environmental Physics (IUP), University of Bremen, Germany

Atmospheric CO2 is the dominant anthropogenic greenhouse gas. Satellite measurements of the CO2 mixing ratio (XCO2) derived from the SCIAMACHY instrument aboard ENVISAT can provide valuable information to quantify regional CO2 sources and sinks. XCO2 can be derived by simultaneously retrieving the atmospheric column of CO2 and O2. Therefore, simulated sun normalized radiance spectra within the O2-A absorption band at around 760nm and of the CO2 band at 1580nm can be fitted to SCIAMACHY measurements. Unfortunately, both bands have a relatively large spectral distance and show also large differences of the strength of absorption. For this reason, path length modifications due to scattering by aerosols and clouds in both bands are also not identical, resulting in possible retrieval errors of XCO2. Sub-visible cirrus clouds with an optical depth of 0.03 can already significantly affect the retrieval. SCIAMACHY measurements within the CO2 band do not hold enough information to correct for this effect. However, valuable information about cirrus clouds can potentially be obtained from SCIAMACHY measurements in the O2-A band. We will present an optimal estimation based retrieval that accounts for cirrus clouds by transferring cirrus information obtained from the O2-A band to the CO2 band.