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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union
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Volume 9, issue 10
Atmos. Meas. Tech., 9, 5227-5238, 2016
https://doi.org/10.5194/amt-9-5227-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.
Atmos. Meas. Tech., 9, 5227-5238, 2016
https://doi.org/10.5194/amt-9-5227-2016
© Author(s) 2016. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 27 Oct 2016

Research article | 27 Oct 2016

Quantification of uncertainties in OCO-2 measurements of XCO2: simulations and linear error analysis

Brian Connor1, Hartmut Bösch2,6, James McDuffie3, Tommy Taylor4, Dejian Fu3, Christian Frankenberg5, Chris O'Dell4, Vivienne H. Payne3, Michael Gunson3, Randy Pollock3, Jonathan Hobbs3, Fabiano Oyafuso3, and Yibo Jiang3 Brian Connor et al.
  • 1BC Scientific Consulting, Stony Brook, NY, USA
  • 2EOS Group, Department of Physics and Astronomy, University of Leicester, Leicester, UK
  • 3Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
  • 4Cooperative Institute for Research in the Atmosphere, Fort Collins, CO, USA
  • 5California Institute of Technology, Pasadena, CA, USA
  • 6National Centre for Earth Observation NCEO, University of Leicester, Leicester, UK

Abstract. We present an analysis of uncertainties in global measurements of the column averaged dry-air mole fraction of CO2 (XCO2) by the NASA Orbiting Carbon Observatory-2 (OCO-2). The analysis is based on our best estimates for uncertainties in the OCO-2 operational algorithm and its inputs, and uses simulated spectra calculated for the actual flight and sounding geometry, with measured atmospheric analyses. The simulations are calculated for land nadir and ocean glint observations. We include errors in measurement, smoothing, interference, and forward model parameters. All types of error are combined to estimate the uncertainty in XCO2 from single soundings, before any attempt at bias correction has been made. From these results we also estimate the "variable error" which differs between soundings, to infer the error in the difference of XCO2 between any two soundings. The most important error sources are aerosol interference, spectroscopy, and instrument calibration. Aerosol is the largest source of variable error. Spectroscopy and calibration, although they are themselves fixed error sources, also produce important variable errors in XCO2. Net variable errors are usually < 1 ppm over ocean and ∼ 0.5–2.0 ppm over land. The total error due to all sources is ∼ 1.5–3.5 ppm over land and ∼ 1.5–2.5 ppm over ocean.

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We present an analysis of uncertainties in global measurements of the column-averaged dry-air mole fraction of CO2 (XCO2) by the satellite OCO-2. The analysis is based on our best estimates for uncertainties in the OCO-2 operational algorithm and its inputs. From these results we estimate the "variable error", which differs between soundings, to infer the error in the difference of XCO2 between any two soundings. Variable errors are usually < 1 ppm over ocean and ~ 0.5–2 ppm over land.
We present an analysis of uncertainties in global measurements of the column-averaged dry-air...
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