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Contribution of the Orbiting Carbon Observatory to the estimation of CO 2 sources and sinks: Theoretical study in a variational data assimilation framework

2007; American Geophysical Union; Volume: 112; Issue: D9 Linguagem: Inglês

10.1029/2006jd007375

2156-2202

Frédéric Chevallier, François‐Marie Bréon, P. J. Rayner,

Climate variability and models

NASA's Orbiting Carbon Observatory will monitor the atmospheric concentrations of carbon dioxide (CO 2 ) along the satellite subtrack over the sunlit hemisphere of the Earth for more than 2 years, starting in late 2008. This paper demonstrates the application of a variational Bayesian formalism to retrieve fluxes at high spatial and temporal resolution from the satellite retrievals. We use a randomization approach to estimate the posterior error statistics of the calculated fluxes. Given our prior information about the fluxes (with error standard deviations about 0.4 g C m −2 d −1 over ocean and 4 g C m −2 d −1 over vegetated areas) and our observation characteristics (with error standard deviations about 2 ppm), we show error reductions of up to about 40% at weekly scale for a grid point of the transport model. We simulate the impact of undetected biases by perturbing the observations and show that regional biases of a few tenths of a part per million in column‐averaged CO 2 can bias the inverted yearly subcontinental fluxes by a few tenths of a gigaton of carbon, which is larger than the uncertainty on the anthropogenic carbon fluxes but smaller than that of natural fluxes over most vegetated areas.