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| Titel |
Assessment of two aerosol optical thickness retrieval algorithms applied to MODIS Aqua and Terra measurements in Europe |
| VerfasserIn |
P. Glantz, M. Tesche |
| 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. 7 ; Nr. 5, no. 7 (2012-07-19), S.1727-1740 |
| Datensatznummer |
250003011
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| Publikation (Nr.) |
 copernicus.org/amt-5-1727-2012.pdf |
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| Zusammenfassung |
| The aim of the present study is to validate AOT (aerosol optical thickness)
and Ångström exponent (α), obtained from MODIS (MODerate
resolution Imaging Spectroradiometer) Aqua and Terra calibrated level 1 data
(1 km horizontal resolution at ground) with the SAER (Satellite AErosol
Retrieval) algorithm and with MODIS Collection 5 (c005) standard product
retrievals (10 km horizontal resolution), against AERONET (AErosol RObotic
NETwork) sun photometer observations over land surfaces in Europe. An
inter-comparison of AOT at 0.469 nm obtained with the two algorithms has
also been performed. The time periods investigated were chosen to enable a
validation of the findings of the two algorithms for a maximal possible
variation in sun elevation. The satellite retrievals were also performed
with a significant variation in the satellite-viewing geometry, since Aqua
and Terra passed the investigation area twice a day for several of the cases
analyzed. The validation with AERONET shows that the AOT at 0.469 and 0.555
nm obtained with MODIS c005 is within the expected uncertainty of one
standard deviation of the MODIS c005 retrievals (ΔAOT = ± 0.05 ± 0.15 · AOT).
The AOT at 0.443 nm retrieved with SAER, but
with a much finer spatial resolution, also agreed reasonably well with
AERONET measurements. The majority of the SAER AOT values are within the
MODIS c005 expected uncertainty range, although somewhat larger average
absolute deviation occurs compared to the results obtained with the MODIS
c005 algorithm. The discrepancy between AOT from SAER and AERONET is,
however, substantially larger for the wavelength 488 nm. This means that the
values are, to a larger extent, outside of the expected MODIS uncertainty
range. In addition, both satellite retrieval algorithms are unable to
estimate α accurately, although the MODIS c005 algorithm performs
better. Based on the inter-comparison of the SAER and MODIS c005 algorithms,
it was found that SAER on the whole is able to obtain results within the
expected uncertainty range of MODIS Aqua and Terra observations. |
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