Preprints
https://doi.org/10.5194/acp-2021-373
https://doi.org/10.5194/acp-2021-373

  11 Aug 2021

11 Aug 2021

Review status: this preprint is currently under review for the journal ACP.

Four years of global carbon cycle observed from OCO-2 version 9 and in situ data, and comparison to OCO-2 v7

Hélène Peiro1, Sean Crowell1, Andrew Schuh2, David F. Baker2, Chris O'Dell2, Andrew R. Jacobson3,4, Frédéric Chevallier5, Junjie Liu6, Annmarie Eldering6, David Crisp6, Feng Deng7, Brad Weir8,9, Sourish Basu10,11, Matthew S. Johnson12, Sajeev Philip13, and Ian Baker14 Hélène Peiro et al.
  • 1University of Oklahoma, Norman, OK, USA
  • 2Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, CO, USA
  • 3Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, CO, USA
  • 4NOAA Global Monitoring Laboratory, Boulder, CO, USA
  • 5Laboratoire des Sciences du Climat et de L’Environnement, LSCE/IPSL, CEA-CNRS-UVSQ,Université Paris-Saclay, 91198 Gif-sur-Yvette, France
  • 6Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
  • 7Department of Physics, University of Toronto, Toronto, Ontario, Canada
  • 8Universities Space Research Association, Columbia, MD, USA
  • 9NASA Goddard Space Flight Center, Greenbelt, MD, USA
  • 10NASA Goddard Space Flight Center, Global Modeling and Assimilation Office, Greenbelt, MD, USA
  • 11Earth System Science Interdisciplinary Center, College Park, MD, USA
  • 12NASA Ames Research Center, Moffett Field, CA, USA
  • 13Universities Space Research Association, Mountain View, CA
  • 14Colorado State University, Atmospheric Sciences, Fort Collins, CO, USA

Abstract. The Orbiting Carbon Observatory 2 (OCO-2) satellite has been provided information to estimate carbon dioxide (CO2) fluxes at global and regional scales since 2014 through the combination of CO2 retrievals with top-down atmospheric inversion methods. Column average CO2 dry air mole fraction retrievals has been constantly improved. A bias correction has been applied in the OCO-2 version 9 retrievals compared to the previous OCO-2 version 7r improving data accuracy and coverage. We study an ensemble of ten atmospheric inversions all characterized by different transport models, data assimilation algorithm and prior fluxes using first OCO-2 v7 in 2015-2016 and then OCO-2 version 9 land observations for the longer period 2015- 2018. Inversions assimilating in situ (IS) measurements have been also used to provide a baseline against which to compare the satellite-driven results. The times series at different scales (going from global to regional scales) of the models emissions are analyzed and compared to each experiments using either OCO-2 or IS data. We then evaluate the inversion ensemble based on dataset from TCCON, aircraft, and in-situ observations, all independent from assimilated data. While we find a similar constraint of global total carbon emissions between the ensemble spread using IS and both OCO-2 retrievals, differences between the two retrieval versions appear over regional scales and particularly in tropical Africa. A difference in the carbon budget between v7 and v9 is found over this region which seems to show the impact of corrections applied in retrievals. However, the lack of data in the tropics limits our conclusions and the estimation of carbon emissions over tropical Africa require further analysis.

Hélène Peiro et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2021-373', Anonymous Referee #2, 07 Sep 2021
    • AC1: 'Reply on RC1', Hélène Peiro, 23 Sep 2021
  • RC2: 'Comment on acp-2021-373', Anonymous Referee #1, 30 Sep 2021

Hélène Peiro et al.

Hélène Peiro et al.

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Short summary
Satellite CO2 observations are constantly improved. We study, from 2015 to 2018, an ensemble of different atmospheric models (inversions) using separately ground-based data or 2 different versions of the OCO-2 satellite. Our study aims to determine if different satellite data corrections can yield different estimates of carbon cycle flux. A difference in the carbon budget between the 2 versions is found over Tropical Africa which seems to show the impact of corrections applied in satellite data.
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