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| Titel |
Assimilation of surface soil moisture into a multilayer soil model: design and evaluation at local scale |
| VerfasserIn |
M. Parrens, J.-F. Mahfouf, A. L. Barbu, J.-C. Calvet |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 18, no. 2 ; Nr. 18, no. 2 (2014-02-19), S.673-689 |
| Datensatznummer |
250120284
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| Publikation (Nr.) |
 copernicus.org/hess-18-673-2014.pdf |
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| Zusammenfassung |
| Land surface models (LSM) have improved considerably in the last two decades.
In this study, the Interactions between Surface,
Biosphere, and Atmosphere (ISBA) LSM soil diffusion scheme is used (with 11 soil
layers represented). A simplified extended Kalman filter (SEKF) allows ground
observations of surface soil moisture (SSM) to be assimilated in the
multilayer LSM in order to constrain deep soil moisture. In parallel, the
same simulations are performed using the ISBA LSM with 2 soil layers (a thin
surface layer and a bulk reservoir). Simulations are performed over a 3 yr
period (2003–2005) for a bare soil field in southwestern France, at the
SMOSREX (Surface Monitoring Of the Soil Reservoir Experiment) site. Analyzed soil moisture values correlate better
with soil moisture observations when the ISBA LSM soil diffusion scheme is
used. The Kalman gain is greater from the surface to 45 cm than below this
limit. For dry periods, corrections introduced by the assimilation scheme
mainly affect the first 15 cm of soil whereas weaker corrections
impact the total soil column for wet periods. Such seasonal corrections
cannot be described by the two-layer ISBA LSM. Sensitivity studies performed
with the multilayer LSM show improved results when SSM (0–6 cm) is
assimilated into the second layer (1–5 cm) than into the first layer
(0–1 cm). The introduction of vertical correlations in the background error
covariance matrix is also encouraging. Using a yearly cumulative distribution function (CDF)-matching scheme for
bias correction instead of matching over the three years permits the seasonal
variability of the soil moisture content to be better transcribed. An
assimilation experiment has also been performed by forcing ISBA-DF (diffusion scheme) with a
local forcing, setting precipitation to zero. This experiment shows the
benefit of the SSM assimilation for correcting inaccurate atmospheric
forcing. |
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