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| Titel |
1D-Var multilayer assimilation of X-band SAR data into a detailed snowpack model |
| VerfasserIn |
X. V. Phan, L. Ferro-Famil, M. Gay, Y. Durand, M. Dumont, S. Morin, S. Allain, G. D'Urso, A. Girard |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1994-0416
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| Digitales Dokument |
URL |
| Erschienen |
In: The Cryosphere ; 8, no. 5 ; Nr. 8, no. 5 (2014-10-27), S.1975-1987 |
| Datensatznummer |
250116331
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| Publikation (Nr.) |
 copernicus.org/tc-8-1975-2014.pdf |
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| Zusammenfassung |
| The structure and physical properties of a snowpack and their temporal
evolution may be simulated using meteorological data and a snow metamorphism
model. Such an approach may meet limitations related to potential divergences
and accumulated errors, to a limited spatial resolution, to wind or
topography-induced local modulations of the physical properties of a snow
cover, etc. Exogenous data are then required in order to constrain the
simulator and improve its performance over time. Synthetic-aperture radars
(SARs) and, in particular, recent sensors provide reflectivity maps of snow-covered
environments with high temporal and spatial resolutions. The radiometric
properties of a snowpack measured at sufficiently high carrier frequencies
are known to be tightly related to some of its main physical parameters, like
its depth, snow grain size and density. SAR acquisitions may then be used,
together with an electromagnetic backscattering model (EBM) able to simulate
the reflectivity of a snowpack from a set of physical descriptors, in order
to constrain a physical snowpack model. In this study, we introduce a
variational data assimilation scheme coupling TerraSAR-X radiometric data
into the snowpack evolution model Crocus. The physical properties of a
snowpack, such as snow density and optical diameter of each layer, are
simulated by Crocus, fed by the local reanalysis of meteorological data
(SAFRAN) at a French Alpine location. These snowpack properties are used as
inputs of an EBM based on dense media
radiative transfer (DMRT) theory, which simulates the total backscattering
coefficient of a dry snow medium at X and higher frequency bands. After
evaluating the sensitivity of the EBM to snowpack parameters, a 1D-Var data
assimilation scheme is implemented in order to minimize the discrepancies
between EBM simulations and observations obtained from TerraSAR-X
acquisitions by modifying the physical parameters of the Crocus-simulated
snowpack. The algorithm then re-initializes Crocus with the modified snowpack
physical parameters, allowing it to continue the simulation of snowpack
evolution, with adjustments based on remote sensing information. This method
is evaluated using multi-temporal TerraSAR-X images acquired over the
specific site of the Argentière glacier (Mont-Blanc massif, French Alps) to
constrain the evolution of Crocus. Results indicate that X-band SAR data can
be taken into account to modify the evolution of snowpack simulated by Crocus. |
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