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| Titel |
Using ocean-glint scattered sunlight as a diagnostic tool for satellite remote sensing of greenhouse gases |
| VerfasserIn |
A. Butz, S. Guerlet, O. P. Hasekamp, A. Kuze, H. Suto |
| 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 ; 6, no. 9 ; Nr. 6, no. 9 (2013-09-27), S.2509-2520 |
| Datensatznummer |
250085071
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| Publikation (Nr.) |
 copernicus.org/amt-6-2509-2013.pdf |
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| Zusammenfassung |
| Spectroscopic measurements of sunlight backscattered by the Earth's surface
is a technique widely used for remote sensing of atmospheric constituent
concentrations from space. Thereby, remote sensing of greenhouse gases poses
particularly challenging accuracy requirements for instrumentation and
retrieval algorithms which, in general, suffer from various error sources.
Here, we investigate a method that helps disentangle sources of error for
observations of sunlight backscattered from the glint spot on the ocean
surface. The method exploits the backscattering characteristics of the ocean
surface, which is bright for glint geometry but dark for off-glint angles.
This property allows for identifying a set of clean scenes where light
scattering due to particles in the atmosphere is negligible such that
uncertain knowledge of the lightpath can be excluded as a source of error. We
apply the method to more than 3 yr of ocean-glint measurements by the
Thermal And Near infrared Sensor for carbon Observation (TANSO) Fourier
Transform Spectrometer (FTS) onboard the Greenhouse Gases Observing Satellite
(GOSAT), which aims at measuring carbon dioxide (CO2) and methane
(CH4) concentrations. The proposed method is able to clearly monitor
recent improvements in the instrument calibration of the oxygen (O2)
A-band channel and suggests some residual uncertainty in our knowledge about
the instrument. We further assess the consistency of CO2 retrievals from
several absorption bands between 6400 cm−1 (1565 nm) and
4800 cm−1 (2100 nm) and find that the absorption bands commonly used
for monitoring of CO2 dry air mole fractions from GOSAT allow for
consistency better than 1.5 ppm. Usage of other bands reveals significant
inconsistency among retrieved CO2 concentrations pointing at
inconsistency of spectroscopic parameters. |
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