Assessing the SMOS Soil Moisture Retrieval Parameters With High-Resolution NAFE'06 Data

The spatial and temporal invariance of Soil Moisture and Ocean Salinity (SMOS) forward model parameters for soil moisture retrieval was assessed at 1-km resolution on a diurnal basis with data from the National Airborne Field Experiment 2006. The approach used was to apply the SMOS default parameter...

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Bibliographic Details
Published in:IEEE geoscience and remote sensing letters 2009-10, Vol.6 (4), p.635-639
Main Authors: Merlin, O., Walker, J.P., Panciera, R., Escorihuela, M.J., Jackson, T.J.
Format: Article
Language:English
Subjects:
Airborne experiment
Area measurement
Bias
calibration
Crops
Detection
Dielectrics
Information retrieval
L-band
L-band radiometry
Mathematical models
Mean square errors
National Airborne Field Experiment (NAFE)
Pixels
Radiometry
Retrieval
retrieval algorithm
Root mean square
SMOS mission
Soil (material)
Soil moisture
Soil Moisture and Ocean Salinity (SMOS)
Soils
Spatial resolution
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Summary:The spatial and temporal invariance of Soil Moisture and Ocean Salinity (SMOS) forward model parameters for soil moisture retrieval was assessed at 1-km resolution on a diurnal basis with data from the National Airborne Field Experiment 2006. The approach used was to apply the SMOS default parameters uniformly over 27 1-km validation pixels, retrieve soil moisture from the airborne observations, and then to interpret the differences between airborne and ground estimates in terms of land use, parameter variability, and sensing depth. For pastures (17 pixels) and nonirrigated crops (5 pixels), the root mean square error (rmse) was 0.03 volumetric (vol./vol.) soil moisture with a bias of 0.004 vol./vol. For pixels dominated by irrigated crops (5 pixels), the rmse was 0.10 vol./vol., and the bias was -0.09 vol./vol. The correlation coefficient between bias in irrigated areas and the 1-km field soil moisture variability was found to be 0.73, which suggests either 1) an increase of the soil dielectric roughness (up to about one) associated with small-scale heterogeneity of soil moisture or/and 2) a difference in sensing depth between an L-band radiometer and the in situ measurements, combined with a strong vertical gradient of soil moisture in the top 6 cm of the soil.
ISSN:1545-598X
1558-0571
DOI:10.1109/LGRS.2009.2012727