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| Titel |
Improvements of synergetic aerosol retrieval for ENVISAT |
| VerfasserIn |
T. Holzer-Popp, M. Schroedter-Homscheidt, H. Breitkreuz, D. Martynenko, L. Klüser |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 8, no. 24 ; Nr. 8, no. 24 (2008-12-18), S.7651-7672 |
| Datensatznummer |
250006525
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| Publikation (Nr.) |
 copernicus.org/acp-8-7651-2008.pdf |
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| Zusammenfassung |
| The synergetic aerosol retrieval method SYNAER (Holzer-Popp et al., 2002a)
has been extended to the use of ENVISAT measurements. It exploits the
complementary information of a radiometer and a spectrometer onboard one
satellite platform to extract aerosol optical depth (AOD) and speciation (as
a choice from a representative set of pre-defined mixtures of water-soluble,
soot, mineral dust, and sea salt components). SYNAER consists of two
retrieval steps. In the first step the radiometer is used for accurate cloud
screening, and subsequently to quantify the aerosol optical depth (AOD) at
550 nm and spectral surface brightness through a dark field technique for
different pre-defined aerosol mixtures. In the second step the spectrometer
is applied to choose the most plausible aerosol mixture through a least
square fit of the measured spectrum with simulated spectra using the
mixture-dependent values of AOD and surface brightness retrieved in the
first step. This method was developed and a first case study evaluation
against few (15) multi-spectral ground-based AERONET sun photometer
observations was conducted with a sensor pair (ATSR-2 and GOME) onboard
ERS-2. Due to instrumental limitations the coverage of SYNAER/ERS-2 is very
sparse. Therefore, SYNAER was transferred to similar sensors AATSR and
SCIAMACHY onboard ENVISAT. While transferring to the new sensor pair
significant improvements in the methodology were made based on a thorough
evaluation of the methodology: (1) an update of the aerosol model, (2)
improved cloud detection in the tropics and sub tropics, and (3) an enhanced
dark field albedo characterization. This paper describes these improvements
in detail and assesses their combined impact on the results. After a brief
assessment of atmospheric noise impact on comparisons of pixel and
station measurements a validation against ground-based measurements establishes
error bars for the SYNAER/ENVISAT method version 2.0. A theoretical analysis
of the information content with regard to aerosol composition (second
retrieval step) is presented to quantify the potential and limitations of
this new capability provided by the SYNAER method. Building on this
analysis, first seasonal and monthly composition results calculated by
applying SYNAER version 2.0 to AATSR and SCIAMACHY are shown to demonstrate
the potential of the approach. An inter-comparison to earlier results of
SYNAER version 1.0 is made for both the validation and the example datasets. |
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