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| Titel |
A method for evaluating bias in global measurements of CO2 total columns from space |
| VerfasserIn |
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, S. C. Wofsy |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 11, no. 23 ; Nr. 11, no. 23 (2011-12-09), S.12317-12337 |
| Datensatznummer |
250010252
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| Publikation (Nr.) |
 copernicus.org/acp-11-12317-2011.pdf |
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| Zusammenfassung |
| 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. |
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