Contribution of the Orbiting Carbon Observatory to the estimation of CO2 sources and sinks: Theoretical study in a variational data assimilation framework
Abstract
NASA's Orbiting Carbon Observatory will monitor the atmospheric concentrations of carbon dioxide (CO2) 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 CO2 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.
- Publication:
-
Journal of Geophysical Research (Atmospheres)
- Pub Date:
- May 2007
- DOI:
- 10.1029/2006JD007375
- Bibcode:
- 2007JGRD..112.9307C
- Keywords:
-
- Biogeosciences: Biogeochemical cycles;
- processes;
- and modeling (0412;
- 0793;
- 1615;
- 4805;
- 4912);
- Biogeosciences: Biosphere/atmosphere interactions (0315);
- Mathematical Geophysics: Inverse theory;
- Biogeosciences: Computational methods and data processing;
- Biogeosciences: Carbon cycling (4806);
- CO<SUB>2</SUB> fluxes;
- inversion;
- satellite