Atmospheric Measurement Techniques (Dec 2018)
Improved retrievals of carbon dioxide from Orbiting Carbon Observatory-2 with the version 8 ACOS algorithm
- C. W. O'Dell,
- A. Eldering,
- P. O. Wennberg,
- D. Crisp,
- M. R. Gunson,
- B. Fisher,
- C. Frankenberg,
- M. Kiel,
- H. Lindqvist,
- L. Mandrake,
- A. Merrelli,
- V. Natraj,
- R. R. Nelson,
- G. B. Osterman,
- V. H. Payne,
- T. E. Taylor,
- D. Wunch,
- B. J. Drouin,
- F. Oyafuso,
- A. Chang,
- J. McDuffie,
- M. Smyth,
- D. F. Baker,
- S. Basu,
- S. Basu,
- F. Chevallier,
- S. M. R. Crowell,
- L. Feng,
- L. Feng,
- P. I. Palmer,
- P. I. Palmer,
- M. Dubey,
- O. E. García,
- D. W. T. Griffith,
- F. Hase,
- L. T. Iraci,
- R. Kivi,
- I. Morino,
- J. Notholt,
- H. Ohyama,
- C. Petri,
- C. M. Roehl,
- M. K. Sha,
- K. Strong,
- R. Sussmann,
- Y. Te,
- O. Uchino,
- V. A. Velazco
Affiliations
- C. W. O'Dell
- Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, CO, USA
- A. Eldering
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- P. O. Wennberg
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
- D. Crisp
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- M. R. Gunson
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- B. Fisher
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- C. Frankenberg
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
- M. Kiel
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
- H. Lindqvist
- Finnish Meteorological Institute, Helsinki, Finland
- L. Mandrake
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- A. Merrelli
- SSEC, University of Wisconsin-Madison, Madison, WI, USA
- V. Natraj
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- R. R. Nelson
- Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, CO, USA
- G. B. Osterman
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- V. H. Payne
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- T. E. Taylor
- Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, CO, USA
- D. Wunch
- Department of Physics, University of Toronto, Toronto, Canada
- B. J. Drouin
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- F. Oyafuso
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- A. Chang
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- J. McDuffie
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- M. Smyth
- Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
- D. F. Baker
- Cooperative Institute for Research in the Atmosphere, Colorado State University, Fort Collins, CO, USA
- S. Basu
- NOAA Earth System Research Laboratory, Global Monitoring Division, Boulder, CO, USA
- S. Basu
- Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, Boulder, Colorado, USA
- F. Chevallier
- Laboratoire des Sciences du Climat et de l'Environnement, IPSL, CEA-CNRS-UVSQ, Gif-sur-Yvette, France
- S. M. R. Crowell
- College of Atmospheric and Geographic Sciences, University of Oklahoma, Norman, OK, USA
- L. Feng
- National Centre for Earth Observation, University of Edinburgh, UK
- L. Feng
- School of GeoSciences, University of Edinburgh, UK
- P. I. Palmer
- National Centre for Earth Observation, University of Edinburgh, UK
- P. I. Palmer
- School of GeoSciences, University of Edinburgh, UK
- M. Dubey
- Los Alamos National Laboratory, Los Alamos, NM, USA
- O. E. García
- Izaña Atmospheric Research Center, Meteorological State Agency of Spain (AEMet), Santa Cruz de Tenerife, Spain
- D. W. T. Griffith
- Centre for Atmospheric Chemistry, University of Wollongong, Wollongong, Australia
- F. Hase
- Karlsruhe Institute of Technology, IMK-ASF, Karlsruhe, Germany
- L. T. Iraci
- NASA Ames Research Center, Moffett Field, CA, USA
- R. Kivi
- Finnish Meteorological Institute, Sodankylä, Finland
- I. Morino
- National Institute for Environmental Studies (NIES), Tsukuba, Japan
- J. Notholt
- Institute of Environmental Physics, University of Bremen, Bremen, Germany
- H. Ohyama
- National Institute for Environmental Studies (NIES), Tsukuba, Japan
- C. Petri
- Institute of Environmental Physics, University of Bremen, Bremen, Germany
- C. M. Roehl
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
- M. K. Sha
- Royal Belgian Institute for Space Aeronomy, Brussels, Belgium
- K. Strong
- Department of Physics, University of Toronto, Toronto, Canada
- R. Sussmann
- Karlsruhe Institute of Technology, IMK-IFU, Garmisch-Partenkirchen, Germany
- Y. Te
- LERMA-IPSL, Sorbonne Université, Observatoire de Paris, Université PSL, CNRS, 75005, Paris, France
- O. Uchino
- National Institute for Environmental Studies (NIES), Tsukuba, Japan
- V. A. Velazco
- Centre for Atmospheric Chemistry, University of Wollongong, Wollongong, Australia
- DOI
- https://doi.org/10.5194/amt-11-6539-2018
- Journal volume & issue
-
Vol. 11
pp. 6539 – 6576
Abstract
Since September 2014, NASA's Orbiting Carbon Observatory-2 (OCO-2) satellite has been taking measurements of reflected solar spectra and using them to infer atmospheric carbon dioxide levels. This work provides details of the OCO-2 retrieval algorithm, versions 7 and 8, used to derive the column-averaged dry air mole fraction of atmospheric CO2 (XCO2) for the roughly 100 000 cloud-free measurements recorded by OCO-2 each day. The algorithm is based on the Atmospheric Carbon Observations from Space (ACOS) algorithm which has been applied to observations from the Greenhouse Gases Observing SATellite (GOSAT) since 2009, with modifications necessary for OCO-2. Because high accuracy, better than 0.25 %, is required in order to accurately infer carbon sources and sinks from XCO2, significant errors and regional-scale biases in the measurements must be minimized. We discuss efforts to filter out poor-quality measurements, and correct the remaining good-quality measurements to minimize regional-scale biases. Updates to the radiance calibration and retrieval forward model in version 8 have improved many aspects of the retrieved data products. The version 8 data appear to have reduced regional-scale biases overall, and demonstrate a clear improvement over the version 7 data. In particular, error variance with respect to TCCON was reduced by 20 % over land and 40 % over ocean between versions 7 and 8, and nadir and glint observations over land are now more consistent. While this paper documents the significant improvements in the ACOS algorithm, it will continue to evolve and improve as the CO2 data record continues to expand.
