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| Titel |
Filling-in of near-infrared solar lines by terrestrial fluorescence and other geophysical effects: simulations and space-based observations from SCIAMACHY and GOSAT |
| VerfasserIn |
J. Joiner, Y. Yoshida, A. P. Vasilkov, E. M. Middleton, P. K. E. Campbell, Y. Yoshida, A. Kuze, L. A. Corp |
| 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 ; 5, no. 4 ; Nr. 5, no. 4 (2012-04-24), S.809-829 |
| Datensatznummer |
250002780
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| Publikation (Nr.) |
 copernicus.org/amt-5-809-2012.pdf |
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| Zusammenfassung |
| Global mapping of terrestrial vegetation fluorescence from space has recently
been accomplished with high spectral resolution
(ν/Δν > 35 000) measurements from the Japanese Greenhouse
gases Observing SATellite (GOSAT). These data are of interest because they
can potentially provide global information on the functional status of
vegetation including light-use efficiency and global primary productivity
that can be used for global carbon cycle modeling. Quantifying the impact of
fluorescence on the O2-A band is important as this band is used for
photon pathlength
characterization in cloud- and aerosol-contaminated pixels
for trace-gas retrievals including
CO2. Here, we examine whether fluorescence information can be derived
from space using potentially lower-cost hyperspectral instrumentation, i.e.,
more than an order of magnitude less spectral resolution
(ν/Δν ~ 1600) than GOSAT, with a relatively simple
algorithm. We discuss laboratory measurements of fluorescence near one of the
few wide and deep solar Fraunhofer lines in the long-wave tail of the
fluorescence emission region, the calcium (Ca) II line at 866 nm that is
observable with a spectral resolution of ~0.5 nm. The filling-in of the
Ca II line due to additive signals from various atmospheric and terrestrial
effects, including fluorescence, is simulated. We then examine filling-in of
this line using the SCanning Imaging Absorption spectroMeter for Atmospheric
CHartographY (SCIAMACHY) satellite instrument. In order to interpret the
satellite measurements, we developed a general approach to correct for
various instrumental artifacts that produce false filling-in of solar lines
in satellite measurements. The approach is applied to SCIAMACHY at the
866 nm Ca II line and to GOSAT at 758 and 770 nm on the shoulders of the
O2-A feature where there are several strong solar Fraunhofer lines that
are filled in primarily by vegetation fluorescence. Finally, we compare
temporal and spatial variations of SCIAMACHY additive signals with those of
GOSAT and the Enhanced Vegetation Index (EVI) from the MODerate-resolution
Imaging Spectroradiometer (MODIS). Although the derived additive signals from
SCIAMACHY are extremely weak at 866 nm, their spatial and temporal
variations are consistent with chlorophyll a fluorescence or another
vegetation-related source. We also show that filling-in occurs at 866 nm
over some barren areas, possibly originating from luminescent minerals in
rock and soil. |
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