Evidence of systematic errors in SCIAMACHY-observed CO 2 due to aerosols

By S. Houweling, W. Hartmann, Ilse Aben, H. Schrijver, J. Skidmore, G. Roelofs, François-Marie Bréon. 2005

171 citations recorded by the source corpus.

Abstract. SCIAMACHY CO2 measurements show a large variability in total column CO2 over the Sahara desert of up to 10%, which is not anticipated from in situ measurements and cannot be explained by results of atmospheric models. Comparisons with colocated aerosol measurements by TOMS and MISR over the Sahara indicate that the seasonal variation of SCIAMACHY-observed CO2 strongly resembles seasonal variations of windblown dust. Correlation coefficients of monthly datasets of colocated MISR aerosol optical depth and SCIAMACHY CO2 vary between 0.6 and 0.8, indicating that about half of the CO2 variance is explained by aerosol optical depth. Radiative transfer model calculations confirm the role of dust and can explain the size of the errors. Sensitivity tests suggest that the remaining variance may largely be explained by variations in the vertical distribution of dust. Further calculations for a few typical aerosol classes and a broad range of atmospheric conditions show that the impact of aerosols on SCIAMACHY retrieved CO2 is by far the largest over the Sahara, but may also reach significant levels elsewhere. Over the continents, aerosols lead mostly to overestimated CO2 columns with the exception of biomass burning plumes and dark coniferous forests. Inverse modelling calculations confirm that aerosol correction of SCIAMACHY CO2 measurements is needed to derive meaningful source and sink estimates. Methods for correcting aerosol-induced errors exist, but so far mainly on the basis of theoretical considerations. As demonstrated by this study, SCIAMACHY may contribute to a verification of such methods using real data.

Subfields: Atmospheric Science, Global and Planetary Change

View Paper: https://www.semanticscholar.org/paper/c06fd963b1a99436f57671748f7a516f4bb6e8d9

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Citations in the corpus

Estimating surface CO 2 fluxes from space-borne CO 2 dry air mole fraction observations using an ensemble Kalman Filter (2008, background): “Uncharac-15 terized systematic and random errors (e.g., Houweling et al., 2005), while the subject of ongoing research (Schneising et al., 2008), limit the application of these data for surface flux estimation.”
The GHGSat-D imaging spectrometer (2020, background): “An analysis of SCIAMACHY retrievals in this same spectral region found that errors decrease for aerosol vertical distributions that are narrow and closer to the Earth’s surface (Houweling et al., 2005).”
Retrieval of atmospheric CO2 with enhanced accuracy and precision from SCIAMACHY: validation with FTS measurements and comparison with model results (2011, methodology): “[5] Several somewhat different XCO2 retrieval algorithms for SCIAMACHY already exist [Buchwitz et al., 2000b; Buchwitz and Burrows, 2004; Buchwitz et al., 2005a, 2005b; Houweling et al., 2005; Barkley et al., 2006a, 2006c, 2006b; Bösch et al., 2006; Barkley et al., 2007; Schneising et al., 2008].”
Contribution of the Orbiting Carbon Observatory to the estimation of CO2 sources and sinks: Theoretical study in a variational data assimilation framework (2007, result): “However, the inversion of existing satellite CO2 products has not been successful so far most likely because of the existence of biases both in the observations and in the transport models [Chevallier et al., 2005a, 2005b;Houweling et al., 2005].”
Space‐based near‐infrared CO2 measurements: Testing the Orbiting Carbon Observatory retrieval algorithm and validation concept using SCIAMACHY observations over Park Falls, Wisconsin (2006, background): “, snow, aerosol scattering can enhance the photon path length due to the strongly forward peaked phase function, which can subsequently bias the retrieval of CO2 [Houweling et al., 2005].”
Atmospheric carbon gases retrieved from SCIAMACHY by WFM-DOAS: version 0.5 CO and CH 4 and impact of calibration improvements on CO 2 retrieval (2006, methodology): “The air columns used to normalize the CO 2 columns are obtained from the simultaneously measured oxygen (O 2 ) columns retrieved from the O 2 A-band (see also Houweling et al., 2005, for SCIAMACHY CO 2 retrieval and van Diedenhoven et al., 2005, for SCIA- MACHY O 2 retrieval).”