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Evaluation and attribution of OCO-2 XCO_2 uncertainties

Worden, John R. and Doran, Gary and Kulawik, Susan and Eldering, Annmarie and Crisp, David and Frankenberg, Christian and O'Dell, Chris and Bowman, Kevin (2017) Evaluation and attribution of OCO-2 XCO_2 uncertainties. Atmospheric Measurement Techniques, 10 (7). pp. 2759-2771. ISSN 1867-8548. doi:10.5194/amt-10-2759-2017.

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Evaluating and attributing uncertainties in total column atmospheric CO_2 measurements (XCO_2) from the OCO-2 instrument is critical for testing hypotheses related to the underlying processes controlling XCO_2 and for developing quality flags needed to choose those measurements that are usable for carbon cycle science. Here we test the reported uncertainties of version 7 OCO-2 XCO_2 measurements by examining variations of the XCO_2 measurements and their calculated uncertainties within small regions (∼  100 km  ×  10.5 km) in which natural CO_2 variability is expected to be small relative to variations imparted by noise or interferences. Over 39 000 of these small neighborhoods comprised of approximately 190 observations per neighborhood are used for this analysis. We find that a typical ocean measurement has a precision and accuracy of 0.35 and 0.24 ppm respectively for calculated precisions larger than  ∼  0.25 ppm. These values are approximately consistent with the calculated errors of 0.33 and 0.14 ppm for the noise and interference error, assuming that the accuracy is bounded by the calculated interference error. The actual precision for ocean data becomes worse as the signal-to-noise increases or the calculated precision decreases below 0.25 ppm for reasons that are not well understood. A typical land measurement, both nadir and glint, is found to have a precision and accuracy of approximately 0.75 and 0.65 ppm respectively as compared to the calculated precision and accuracy of approximately 0.36 and 0.2 ppm. The differences in accuracy between ocean and land suggests that the accuracy of XCO2 data is likely related to interferences such as aerosols or surface albedo as they vary less over ocean than land. The accuracy as derived here is also likely a lower bound as it does not account for possible systematic biases between the regions used in this analysis.

Item Type:Article
Related URLs:
URLURL TypeDescription
Worden, John R.0000-0003-0257-9549
Eldering, Annmarie0000-0003-1080-9922
Crisp, David0000-0002-4573-9998
Frankenberg, Christian0000-0002-0546-5857
Bowman, Kevin0000-0002-8659-1117
Alternate Title:Evaluation and attribution of OCO-2 XCO2 uncertainties
Additional Information:© 2017 Author(s). This work is distributed under the Creative Commons Attribution 3.0 License. Published by Copernicus Publications on behalf of the European Geosciences Union. Received: 23 May 2016 – Discussion started: 21 Jul 2016 - Revised: 23 Jun 2017 – Accepted: 29 Jun 2017 – Published: 31 Jul 2017. Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Funding for Susan Kulawik provided by NASA Roses NMO710771/NNN13D771T, “Assessing OCO-2 predicted sensitivity and errors”. The authors declare that they have no conflict of interest.
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Issue or Number:7
Record Number:CaltechAUTHORS:20180319-133611406
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Official Citation:Worden, J. R., Doran, G., Kulawik, S., Eldering, A., Crisp, D., Frankenberg, C., O'Dell, C., and Bowman, K.: Evaluation and attribution of OCO-2 XCO2 uncertainties, Atmos. Meas. Tech., 10, 2759-2771,, 2017
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:85361
Deposited By: Tony Diaz
Deposited On:26 Mar 2018 22:19
Last Modified:15 Nov 2021 20:28

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