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Discussion papers
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 19 Dec 2019

Submitted as: research article | 19 Dec 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).

The potential of OCO-2 data to reduce the uncertainties in CO2 surface fluxes over Australia using a variational assimilation scheme

Yohanna Villalobos1,2, Peter Rayner1,2, Steven Thomas1, and Jeremy Silver1 Yohanna Villalobos et al.
  • 1School of Earth Sciences, University of Melbourne, Australia
  • 2ARC Centre of Excellence for Climate Extremes, Sydney, Australia

Abstract. This paper addresses the question of how much uncertainties in CO2 fluxes over Australia can be reduced by assimilation of total-column carbon dioxide retrievals from the Orbiting Carbon Observatory-2 (OCO-2) satellite instrument. We apply a four-dimensional variational data assimilation system, based around the Community Multiscale Air Quality (CMAQ) transport-dispersion model. We ran a series of observing system simulation experiments to estimate posterior error statistics of optimized monthly mean CO2 fluxes in Australia. Our assimilations were run with a horizontal grid resolution of 81 km using OCO-2 data for 2015. We found that on average, the total Australia flux uncertainty was reduced by up to 40 % using only OCO-2 nadir measurements. Using both nadir and glint satellite measurements produces uncertainty reductions up to 80 %, which represents 0.55 PgC y−1 for the whole continent. Uncertainty reductions were found to be greatest in the more productive regions of Australia. The choice of the correlation structure in the prior error covariance was found to play a large role in distributing information from the observations. Overall the results suggest that flux inversions at this unusually fine scale will yield useful information on the Australian carbon cycle.

Yohanna Villalobos et al.
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Yohanna Villalobos et al.
Yohanna Villalobos et al.
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Short summary
Estimated carbon fluxes for Australia are subject to considerable uncertainty. We ran simulation experiments over Australia to determine how much these uncertainties can be constrained using satellite data. We found that the satellite data has the potential to reduce these uncertainties up to 80 % across the whole continent. For one month, this percentage corresponds to 0.55 PgC y−1 for Australia. This method could lead to significantly more accurate estimates of Australia's carbon budget.
Estimated carbon fluxes for Australia are subject to considerable uncertainty. We ran simulation...