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Measuring atmospheric CO2 from space using Full Spectral Initiation (FSI) WFM-DOAS

Paul Monks(1) and Paul Monks(2)

(1) University of Leicester, , LE1 7RH , Leicester, United Kingdom
(2) University of Leicester, Leicester University, LE1 7RH, Leicester , United Kingdom


Satellite measurements of the atmospheric CO2 concentration is a rapidly evolving area of scientific research which can help reduce the uncertainties in the global carbon cycle fluxes and provide insight into surface sources and sinks. One of the emerging CO2 measurement techniques is a relatively new retrieval algorithm called Weighting Function Modified Differential Optical Absorption Spectroscopy (WFM-DOAS) developed by Buchwitz et al., (2000). This algorithm is designed to measure the total columns of CO2 (and other greenhouse gases) through the application to spectral measurements in the near–infrared (NIR), made by the SCIAMACHY instrument on-board ENVISAT. The algorithm itself is based on fitting the logarithm of a model reference spectrum and its derivatives to the logarithm of the ratio of a measured nadir radiance and solar irradiance spectrum. A detailed error assessment of this technique has been conducted and it has been found necessary to include suitable a priori information within the retrieval in order to minimize the errors on the retrieved CO2 columns. Hence, we introduce a new CO2 retrieval algorithm called Full Spectral Initiation (FSI) WFM-DOAS which generates a reference spectrum for each individual SCIAMACHY observation using the known properties of the atmosphere and surface the time of the measurement. Initial retrievals over Siberia and North America, for the year 2003, show that the measured CO2 columns are not biased from the input a priori data and that whilst the monthly averaged CO2 distributions contain a high degree of variability, they also contain significant spatial features. Comparisons to ground based FTIR data and the TM3 chemical transport model (Heimann and Körner, 2003) are also presented.


Buchwitz, M., Rozanov, V.V and Burrows J.P., 2000, A near infrared optimised DOAS method for the fast global retrieval of atmospheric CH4, CO, CO2, H2O and N2O total column amounts from SCIAMACHY / ENVISAT-1 nadir radiances, J. Geophys. Res. 105, 15231-15246

Heimann, M. and Körner, S.: The Global Atmospheric Tracer Model TM3, Model Description 25 and Users Manual Release 3.8a, Tech. Rep. 5, Max Planck Institute for Biogeochemistry (MPI-BGC), Jena, Germany, 2003.


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Full paper

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry