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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-1235
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
10 Jan 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
A comparison of atmospheric CO2 flux signals obtained from GEOS-Chem flux inversions constrained by in situ or GOSAT observations
Saroja M. Polavarapu1, Feng Deng2, Brendan Byrne2, Dylan B. A. Jones2, and Micheal Neish1 1Climate Research Division, Environment and Climate Change Canada, Toronto, Ontario, M3H 5T4, Canada
2Dept. of Physics, University of Toronto, Toronto, Ontario, M5S 1A7, Canada
Abstract. The CO2 flux signal is defined as the difference of the four-dimensional CO2 field obtained by integrating an atmospheric transport model with posterior fluxes and that obtained with prior fluxes. It is a function of both the model and the prior fluxes and it can provide insight into how posterior fluxes inform CO2 distributions. Here, we use the GEOS-Chem transport model constrained by either GOSAT or in situ observations to obtain two sets of posterior flux estimates in order to compare the flux signals obtained from the two different observing systems. Flux signals are also computed using two different models. The global flux signal in the troposphere primarily reflects the northern extratropics whereas the global flux signal in the stratosphere mainly reflects tropical contributions. While both observing systems constrain the global budget for 2010 equally well, stronger seasonal variations of the flux signal are obtained with GOSAT. Posterior CO2 distributions obtained with in situ observations better agree with TCCON measurements over an 18-month time period, but GOSAT-informed posterior fluxes better constrain the seasonal cycle at northern extratropical sites. Zonal standard deviations of the flux signal exceed the minimal value (defined by uncertainty in meteorological analyses) through most of the year when GOSAT observations are used, but when in situ observations are used, the minimum value is exceeded only in boreal summer. This indicates a potential for flux estimates constrained by GOSAT data to retrieve spatial structures within a zonal band throughout the year in the tropics and through most of the year in the northern extratropics. Verification of such spatial structures will require a dense network of independent observations.

Citation: Polavarapu, S. M., Deng, F., Byrne, B., Jones, D. B. A., and Neish, M.: A comparison of atmospheric CO2 flux signals obtained from GEOS-Chem flux inversions constrained by in situ or GOSAT observations, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-1235, in review, 2018.
Saroja M. Polavarapu et al.
Saroja M. Polavarapu et al.
Saroja M. Polavarapu et al.

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Short summary
A new diagnostic reveals how fluxes constrained by two different CO2 observing systems inform atmospheric CO2 simulations. The potential for GOSAT data to better resolve zonally asymmetric structures in the tropics year round and in the northern extratropics in most seasons is shown. Using in situ data yields better a match to independent observations on the global, annual scale. Such complementarity of the observing systems can be exploited in greenhouse gas data assimilation systems.
A new diagnostic reveals how fluxes constrained by two different CO2 observing systems inform...
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