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| Titel |
Quantification and mitigation of the impact of scene inhomogeneity on Sentinel-4 UVN UV-VIS retrievals |
| VerfasserIn |
S. Noël, K. Bramstedt, H. Bovensmann, K. Gerilowski, J. P. Burrows, C. Standfuss, E. Dufour, B. Veihelmann |
| 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. 6 ; Nr. 5, no. 6 (2012-06-11), S.1319-1331 |
| Datensatznummer |
250002967
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| Publikation (Nr.) |
 copernicus.org/amt-5-1319-2012.pdf |
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| Zusammenfassung |
| The quality of trace gas products derived from measurements of a space-borne
imaging spectrometer is affected by the inhomogeneity of the illumination of
the instrument slit and thus by the heterogeneity of the observed scene. This
paper aims to quantify this effect and summarise findings on how to mitigate
the impact of inhomogeneous slit illumination on tropospheric O3,
NO2, SO2 and HCHO columns derived from measurements of the
Sentinel-4 UVN imaging spectrometer. For this purpose, spectra for
inhomogeneous ground scenes have been simulated based on a combination of a
radiative transfer model and spatially high resolved MODIS (Moderate
Resolution Imaging Spectroradiometer) data. The resulting errors on
tropospheric O3, NO2, SO2 and HCHO columns derived from these
spectra have been determined via an optimal estimation approach. We conclude
that inhomogeneous illumination results in significant errors in the data
products if the natural inhomogeneity of the observed scenes are not accounted
for. O3 columns are less affected than the other data products; largest
errors occur for NO2 (mean absolute errors about 5%, maximum error
exceeding 50%, standard deviation of the errors about 8%). These errors
may be significantly reduced (by factors up to about 10) by an appropriate
wavelength calibration applied individually to each Earthshine radiance
spectrum. With wavelength calibration the estimated mean absolute errors due
to inhomogeneity are for all gases well below 1%; standard deviations of
the errors are 1.5% or lower; maximum errors are about 10% for NO2
and around 5% for the other gases. |
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