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| Titel |
The impact of spectral resolution on satellite retrieval accuracy of CO2 and CH4 |
| VerfasserIn |
A. Galli, S. Guerlet, A. Butz, I. Aben, H. Suto, A. Kuze, N. M. Deutscher, J. Notholt, D. Wunch, P. O. Wennberg, D. W. T. Griffith, O. Hasekamp, J. Landgraf |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 7, no. 4 ; Nr. 7, no. 4 (2014-04-29), S.1105-1119 |
| Datensatznummer |
250115704
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| Publikation (Nr.) |
 copernicus.org/amt-7-1105-2014.pdf |
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| Zusammenfassung |
The Fourier-transform spectrometer on board the Japanese GOSAT (Greenhouse gases Observing SATellite) satellite
offers an excellent opportunity to study the impact of instrument resolution
on retrieval accuracy of CO2 and CH4. This is relevant to further
improve retrieval accuracy and to optimize the cost–benefit ratio of future
satellite missions for the remote sensing of greenhouse gases. To address
this question, we degrade GOSAT measurements with a spectral resolution of
≈ 0.24 cm−1 step by step to a resolution of 1.5 cm−1. We
examine the results by comparing relative differences at various resolutions,
by referring the results to reference values from the Total Carbon Column
Observing Network (TCCON), and by calculating and inverting synthetic spectra
for which the true CO2 and CH4 columns are known. The main impacts
of degrading the spectral resolution are reproduced for all approaches based
on GOSAT measurements; pure forward model errors identified with simulated
measurements are much smaller.
For GOSAT spectra, the most notable effect on CO2 retrieval accuracy is
the increase of the standard deviation of retrieval errors from 0.7 to
1.0% when the spectral resolution is reduced by a factor of six. The
retrieval biases against atmospheric water abundance and air mass become
stronger with decreasing resolution. The error scatter increase for CH4
columns is less pronounced. The selective degradation of single spectral
windows demonstrates that the retrieval accuracy of CO2 and CH4 is
dominated by the spectral range where the absorption lines of the target
molecule are located. For both GOSAT and synthetic measurements, retrieval
accuracy decreases with lower spectral resolution for a given signal-to-noise
ratio, suggesting increasing interference errors. |
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