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| Titel |
A sea surface reflectance model for (A)ATSR, and application to aerosol retrievals |
| VerfasserIn |
A. M. Sayer, G. E. Thomas, R. G. Grainger |
| 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 ; 3, no. 4 ; Nr. 3, no. 4 (2010-07-05), S.813-838 |
| Datensatznummer |
250001203
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| Publikation (Nr.) |
 copernicus.org/amt-3-813-2010.pdf |
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| Zusammenfassung |
| A model of the sea surface bidirectional reflectance distribution function
(BRDF) is presented for the visible and near-IR channels (over the spectral
range 550 nm to 1.6 μm) of the dual-viewing Along-Track Scanning
Radiometers (ATSRs). The intended application is as part of the Oxford-RAL
Aerosols and Clouds (ORAC) retrieval scheme. The model accounts for
contributions to the observed reflectance from whitecaps, sun-glint and
underlight. Uncertainties in the parametrisations used in the BRDF model are
propagated through into the forward model and retrieved state. The new BRDF
model offers improved coverage over previous methods, as retrievals are
possible into the sun-glint region, through the ATSR dual-viewing system. The
new model has been applied in the ORAC aerosol retrieval algorithm to process
Advanced ATSR (AATSR) data from September 2004 over the south-eastern
Pacific. The assumed error budget is shown to be generally appropriate,
meaning the retrieved states are consistent with the measurements and a
priori assumptions. The resulting field of aerosol optical depth (AOD) is
compared with colocated MODIS-Terra observations, AERONET observations at
Tahiti, and cruises over the oceanic region. MODIS and AATSR show similar
spatial distributions of AOD, although MODIS reports values which are larger
and more variable. It is suggested that assumptions in the MODIS aerosol
retrieval algorithm may lead to a positive bias in MODIS AOD of order 0.01 at
550 nm over ocean regions where the wind speed is high. |
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