Articles | Volume 11, issue 23
https://doi.org/10.5194/acp-11-12317-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.
https://doi.org/10.5194/acp-11-12317-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article |
|
09 Dec 2011
A method for evaluating bias in global measurements of CO2 total columns from space
D. Wunch, P. O. Wennberg, G. C. Toon, B. J. Connor, B. Fisher, G. B. Osterman, C. Frankenberg, L. Mandrake, C. O'Dell, P. Ahonen, S. C. Biraud, R. Castano, N. Cressie, D. Crisp, N. M. Deutscher, A. Eldering, M. L. Fisher, D. W. T. Griffith, M. Gunson, P. Heikkinen, G. Keppel-Aleks, E. Kyrö, R. Lindenmaier, R. Macatangay, J. Mendonca, J. Messerschmidt, C. E. Miller, I. Morino, J. Notholt, F. A. Oyafuso, M. Rettinger, J. Robinson, C. M. Roehl, R. J. Salawitch, V. Sherlock, K. Strong, R. Sussmann, T. Tanaka, D. R. Thompson, O. Uchino, T. Warneke, and S. C. Wofsy
California Institute of Technology, Pasadena, CA, USA
California Institute of Technology, Pasadena, CA, USA
California Institute of Technology, Pasadena, CA, USA
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
BC Consulting, Ltd., Alexandra, New Zealand
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Colorado State University, Fort Collins, CO, USA
Arctic Research Centre of the Finnish Meteorological Institute, Helsinki, Finland
Lawrence Berkeley National Laboratories, Berkeley, CA, USA
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Department of Statistics, The Ohio State University, Columbus, OH, USA
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
University of Bremen, Bremen, Germany
University of Wollongong, Wollongong, NSW, Australia
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Lawrence Berkeley National Laboratories, Berkeley, CA, USA
University of Wollongong, Wollongong, NSW, Australia
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
Arctic Research Centre of the Finnish Meteorological Institute, Helsinki, Finland
California Institute of Technology, Pasadena, CA, USA
Arctic Research Centre of the Finnish Meteorological Institute, Helsinki, Finland
Department of Physics, University of Toronto, Toronto, ON, Canada
University of Wollongong, Wollongong, NSW, Australia
Department of Physics, University of Toronto, Toronto, ON, Canada
University of Bremen, Bremen, Germany
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
National Institute for Environmental Studies, Tsukuba, Japan
University of Bremen, Bremen, Germany
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
IMK-IFU, Garmisch-Partenkirchen, Germany
National Institute of Water & Atmospheric Research, Wellington, New Zealand
California Institute of Technology, Pasadena, CA, USA
Atmospheric & Oceanic Science, University of Maryland, College Park, MD, USA
National Institute of Water & Atmospheric Research, Wellington, New Zealand
Department of Physics, University of Toronto, Toronto, ON, Canada
IMK-IFU, Garmisch-Partenkirchen, Germany
National Institute for Environmental Studies, Tsukuba, Japan
now at: Japan Aerospace Exploration Agency, Tsukuba, Japan
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
National Institute for Environmental Studies, Tsukuba, Japan
University of Bremen, Bremen, Germany
Harvard University, Cambridge, MA, USA
Abstract. We describe a method of evaluating systematic errors in measurements of total column dry-air mole fractions of CO2 (XCO2) from space, and we illustrate the method by applying it to the v2.8 Atmospheric CO2 Observations from Space retrievals of the Greenhouse Gases Observing Satellite (ACOS-GOSAT) measurements over land. The approach exploits the lack of large gradients in XCO2 south of 25° S to identify large-scale offsets and other biases in the ACOS-GOSAT data with several retrieval parameters and errors in instrument calibration. We demonstrate the effectiveness of the method by comparing the ACOS-GOSAT data in the Northern Hemisphere with ground truth provided by the Total Carbon Column Observing Network (TCCON). We use the observed correlation between free-tropospheric potential temperature and XCO2 in the Northern Hemisphere to define a dynamically informed coincidence criterion between the ground-based TCCON measurements and the ACOS-GOSAT measurements. We illustrate that this approach provides larger sample sizes, hence giving a more robust comparison than one that simply uses time, latitude and longitude criteria. Our results show that the agreement with the TCCON data improves after accounting for the systematic errors, but that extrapolation to conditions found outside the region south of 25° S may be problematic (e.g., high airmasses, large surface pressure biases, M-gain, measurements made over ocean). A preliminary evaluation of the improved v2.9 ACOS-GOSAT data is also discussed.
How to cite. Wunch, D., Wennberg, P. O., Toon, G. C., Connor, B. J., Fisher, B., Osterman, G. B., Frankenberg, C., Mandrake, L., O'Dell, C., Ahonen, P., Biraud, S. C., Castano, R., Cressie, N., Crisp, D., Deutscher, N. M., Eldering, A., Fisher, M. L., Griffith, D. W. T., Gunson, M., Heikkinen, P., Keppel-Aleks, G., Kyrö, E., Lindenmaier, R., Macatangay, R., Mendonca, J., Messerschmidt, J., Miller, C. E., Morino, I., Notholt, J., Oyafuso, F. A., Rettinger, M., Robinson, J., Roehl, C. M., Salawitch, R. J., Sherlock, V., Strong, K., Sussmann, R., Tanaka, T., Thompson, D. R., Uchino, O., Warneke, T., and Wofsy, S. C.: A method for evaluating bias in global measurements of CO2 total columns from space, Atmos. Chem. Phys., 11, 12317–12337, https://doi.org/10.5194/acp-11-12317-2011, 2011.
Received: 28 Jun 2011 – Discussion started: 22 Jul 2011 – Revised: 21 Nov 2011 – Accepted: 24 Nov 2011 – Published: 09 Dec 2011