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| Titel |
Towards an optimal fusion of SMOS and Aquarius SSS data |
| VerfasserIn |
Sebastien Guimbard, Marta Umbert, Antonio Turiel, Marcos Portabella |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250099999
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| Publikation (Nr.) |
 EGU/EGU2014-15863.pdf |
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| Zusammenfassung |
| The European Space Agency (ESA) Soil Moisture and Ocean Salinity (SMOS) mission was
launched in November 2009, carrying onboard the MIRAS instrument, a novel
fully-polarimetric L-band radiometer which estimates the surface brightness temperature
(TB) by means of two-dimensional aperture synthesis interferometry. In June 2011, the
National Aeronautics and Space Administration (NASA) and Argentina’s Space Agency
(CONAE) launched the Aquarius/SAC-D mission carrying onboard an L-band real aperture
radiometer together with an L-band scatterometer. These two missions provide
global coverage of sea surface salinity (SSS) with different repetition rates, spatial
resolutions and accuracies. While SMOS has a wider coverage and higher spatial
resolution, Aquarius has higher radiometric accuracy. To achieve the challenging mission
requirements at weekly (0.1 psu at 200 x 200 km resolution) and monthly (0.1
psu at 100 km x 100 km resolution) scales, fusion of SMOS and Aquarius SSS is
required.
A prerequisite for a successful data fusion is to perform a comprehensive intercalibration
of the different SSS data sources. The SMOS and Aquarius instrument concepts are very
different and, as such, we expect different calibration strategies as well as different impact of
external noise contaminations (e.g., Sun, land-sea contamination, radio frequency
interference, etc.). These differences will of course produce differences in the SMOS and
Aquarius SSS retrievals. Despite these differences, both instruments measure the brightness
temperature of the ocean surface at the same frequency (1.41 GHz) and polarizations (except
for the Stokes 4 parameter which is not measured by Aquarius). As such, the theoretical
relation between the brightness temperature and the different sea surface geophysical
parameters (including SSS) is the same for both missions. In consequence, one would expect
that by doing proper calibration and external noise corrections/filtering, SMOS and Aquarius
SSS could be straightforwardly merged. However, this is not true since SMOS and Aquarius
SSS retrieval algorithms differ and such differences lead to non-negligible differences in the
derived SSS maps. This can be shown by simply analyzing the differences between the
different products (i.e., different SSS retrieval algorithms) available for each mission
separately.
In this work, a thorough assessment of the impact of using different auxiliary data (e.g.,
sea surface winds: ECMWF, NCEP, Aquarius scatterometer; sea surface temperature:
Reynolds, OSTIA), different forward models (galactic, dielectric constant, and roughness
models), and different retrieval approaches (multiparametric Bayesian inversion, direct
retrievals by forward propagation to TB corrections for TEC, galaxy, and roughness) on the
final SSS maps is carried out. This analysis sets the grounds for an optimal fusion of SMOS
and Aquarius SSS data. |
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