The OCO‐2 and OCO‐3 ACOS Version 11 XCO 2 Data Products: A Benchmark Record for Space‐Based Global Carbon Cycle Research

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Abstract
NASA's Orbiting Carbon Observatory‐2 (OCO‐2) and OCO‐3 have been observing Earth's atmosphere from space since September 2014 and August 2019, respectively. The version 11 (v11) Atmospheric Carbon Observations from Space (ACOS) Level 2 full physics (L2FP) retrieval algorithm has been used to provide estimates of the column‐averaged dry‐air mole fraction of carbon dioxide () from OCO measurements of surface reflected near‐infrared solar radiation. In this work, updates to the ACOS v11 retrieval algorithm are discussed, and the quality filtering and bias correction of the products are described. estimates from OCO‐2 and OCO‐3 are compared to Total Carbon Column Observing Network (TCCON) observations and to atmospheric inversion models, which serve as truth‐proxies for . In addition, a direct comparison of collocated soundings between OCO‐2 and OCO‐3 is performed. Variations in v11 over small areas show improvement in agreement between actual and theoretical uncertainties, suggesting a reduction in systematic errors compared to v10, especially for OCO‐3. There is reduced variance in the new v11 product relative to truth‐proxies, including less divergence in the values with time against models. The collocations of observations between OCO‐2 and OCO‐3 indicate an overall mean difference of <0.2 ppm across the overlapping time range. Furthermore, OCO‐2 and OCO‐3 agree better with each other than they do with the validation sources, suggesting a well conditioned and unified set of concentrations that can be used concurrently for carbon cycle studies to provide a benchmark record spanning September 2014 through August 2026.
Funding Information
  • Jet Propulsion Laboratory
  • National Centre for Earth Observation

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