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| Titel |
Spatial and temporal variability of biophysical variables in southwestern France from airborne L-band radiometry |
| VerfasserIn |
E. Zakharova, J.-C. Calvet, S. Lafont, C. Albergel, J.-P. Wigneron, M. Pardé, Y. Kerr, M. Zribi |
| 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 ; 16, no. 6 ; Nr. 16, no. 6 (2012-06-25), S.1725-1743 |
| Datensatznummer |
250013331
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| Publikation (Nr.) |
 copernicus.org/hess-16-1725-2012.pdf |
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| Zusammenfassung |
| In 2009 and 2010 the L-band microwave Cooperative Airborne Radiometer for
Ocean and Land Studies (CAROLS) campaign was performed in southwestern
France to support the calibration and validation of the new Soil Moisture
and Ocean Salinity (SMOS) satellite mission. The L-band Microwave Emission
of the Biosphere (L-MEB) model was used to retrieve surface soil moisture
(SSM) and the vegetation optical depth (VOD) from the CAROLS brightness
temperature measurements. The CAROLS SSM was compared with in situ
observations at 11 sites of the SMOSMANIA (Soil Moisture Observing
System-Meteorological Automatic Network Integrated Application) network of
Météo-France. For eight of them, significant correlations were
observed (0.51 ≤ r ≤ 0.82), with standard deviation of differences
ranging from 0.039 m3 m−3 to 0.141 m3 m−3. Also, the
CAROLS SSM was compared with SSM values simulated by the A-gs version of the
Interactions between Soil, Biosphere and Atmosphere (ISBA-A-gs) model along
20 flight lines, at a resolution of 8 km × 8 km. A significant
spatial correlation between these two datasets was observed for all the
flights (0.36 ≤ r ≤ 0.85). The CAROLS VOD presented significant spatial
correlations with the vegetation water content (VWC) derived from the
spatial distribution of vegetation types used in ISBA-A-gs and from the Leaf
Area Index (LAI) simulated for low vegetation. On the other hand, the CAROLS
VOD presented little temporal changes, and no temporal correlation was
observed with the simulated LAI. For low vegetation, the ratio of VOD to VWC
tended to decrease, from springtime to summertime. The ISBA-A-gs grid cells
(8 km × 8 km) were sampled every 5 m by CAROLS observations,
at a spatial resolution of about 2 km.
For 83% of the grid cells, the standard
deviation of the sub-grid CAROLS SSM was lower than 0.05 m3 m−3. The presence of small water
bodies within the ISBA-A-gs grid cells tended to increase the CAROLS SSM
spatial variability, up to 0.10 m3 m−3. Also, the grid cells
characterised by a high vegetation cover heterogeneity presented higher
standard deviation values, for both SSM and VOD. |
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