A Time-Series Approach to Estimating Soil Moisture From Vegetated Surfaces Using L-Band Radar Backscatter

Many previous studies have shown the sensitivity of radar backscatter to surface soil moisture content, particularly at L-band. Moreover, the estimation of soil moisture from radar for bare soil surfaces is well-documented, but estimation underneath a vegetation canopy remains unsolved. Vegetation s...

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Bibliographic Details
Published in:IEEE transactions on geoscience and remote sensing 2017-06, Vol.55 (6), p.3186-3193
Main Authors: Ouellette, Jeffrey D., Johnson, Joel T., Balenzano, Anna, Mattia, Francesco, Satalino, Giuseppe, Seung-Bum Kim, Dunbar, R. Scott, Colliander, Andreas, Cosh, Michael H., Caldwell, Todd G., Walker, Jeffrey P., Berg, Aaron A.
Format: Article
Language:English
Subjects:
Algorithms
Backscatter
Backscattering
Change detection
Data
Detection
Electromagnetic scattering
Estimation
Forward scattering
Land cover
Modelling
Moisture content
Optical measuring instruments
Parameter estimation
Plant cover
Radar
Radiometers
remote sensing
Satellite-borne radar
Satellites
Scattering
Soil
Soil moisture
Soil surfaces
Vegetation
Vegetation mapping
Water content
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Summary:Many previous studies have shown the sensitivity of radar backscatter to surface soil moisture content, particularly at L-band. Moreover, the estimation of soil moisture from radar for bare soil surfaces is well-documented, but estimation underneath a vegetation canopy remains unsolved. Vegetation significantly increases the complexity of modeling the electromagnetic scattering in the observed scene, and can even obstruct the contributions from the underlying soil surface. Existing approaches to estimating soil moisture under vegetation using radar typically rely on a forward model to describe the backscattered signal and often require that the vegetation characteristics of the observed scene be provided by an ancillary data source. However, such information may not be reliable or available during the radar overpass of the observed scene (e.g., due to cloud coverage if derived from an optical sensor). Thus, the approach described herein is an extension of a change-detection method for soil moisture estimation, which does not require ancillary vegetation information, nor does it make use of a complicated forward scattering model. Novel modifications to the original algorithm include extension to multiple polarizations and a new technique for bounding the radar-derived soil moisture product using radiometer-based soil moisture estimates. Soil moisture estimates are generated using data from the Soil Moisture Active/Passive (SMAP) satellite-borne radar and radiometer data, and are compared with up-scaled data from a selection of in situ networks used in SMAP validation activities. These results show that the new algorithm can consistently achieve rms errors less than 0.07 m 3 /m 3 over a variety land cover types.
ISSN:0196-2892
1558-0644
DOI:10.1109/TGRS.2017.2663768