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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
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Volume 13, issue 17
Atmos. Chem. Phys., 13, 8695-8717, 2013
https://doi.org/10.5194/acp-13-8695-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Chem. Phys., 13, 8695-8717, 2013
https://doi.org/10.5194/acp-13-8695-2013
© Author(s) 2013. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 03 Sep 2013

Research article | 03 Sep 2013

Global CO2 fluxes estimated from GOSAT retrievals of total column CO2

S. Basu1,2, S. Guerlet1, A. Butz3, S. Houweling1,2, O. Hasekamp1, I. Aben1, P. Krummel4, P. Steele4, R. Langenfelds4, M. Torn5, S. Biraud5, B. Stephens6, A. Andrews7, and D. Worthy8 S. Basu et al.
  • 1SRON Netherlands Institute for Space Research, Utrecht, the Netherlands
  • 2Institute for Marine & Atmospheric Research, Utrecht University, Utrecht, the Netherlands
  • 3IMK-ASF, Karlsruhe Institute of Technology, Karlsruhe, Germany
  • 4Commonwealth Scientific and Industrial Research Organisation, Victoria, Australia
  • 5Lawrence Berkeley National Laboratory, California, USA
  • 6National Center for Atmospheric Research, Colorado, USA
  • 7National Oceanic and Atmospheric Administration, Colorado, USA
  • 8Environment Canada, Toronto, Canada

Abstract. We present one of the first estimates of the global distribution of CO2 surface fluxes using total column CO2 measurements retrieved by the SRON-KIT RemoTeC algorithm from the Greenhouse gases Observing SATellite (GOSAT). We derive optimized fluxes from June 2009 to December 2010. We estimate fluxes from surface CO2 measurements to use as baselines for comparing GOSAT data-derived fluxes. Assimilating only GOSAT data, we can reproduce the observed CO2 time series at surface and TCCON sites in the tropics and the northern extra-tropics. In contrast, in the southern extra-tropics GOSAT XCO2 leads to enhanced seasonal cycle amplitudes compared to independent measurements, and we identify it as the result of a land–sea bias in our GOSAT XCO2 retrievals. A bias correction in the form of a global offset between GOSAT land and sea pixels in a joint inversion of satellite and surface measurements of CO2 yields plausible global flux estimates which are more tightly constrained than in an inversion using surface CO2 data alone. We show that assimilating the bias-corrected GOSAT data on top of surface CO2 data (a) reduces the estimated global land sink of CO2, and (b) shifts the terrestrial net uptake of carbon from the tropics to the extra-tropics. It is concluded that while GOSAT total column CO2 provide useful constraints for source–sink inversions, small spatiotemporal biases – beyond what can be detected using current validation techniques – have serious consequences for optimized fluxes, even aggregated over continental scales.

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