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@PHDTHESIS{Jonard:132075,
      author       = {Jonard, Francois},
      title        = {{S}oil water content estimation using ground-based active
                      and passive microwave remote sensing: ground-penetrating
                      radar and radiometer},
      school       = {Université catholique de Louvain (Belgium)},
      type         = {Dr.},
      address      = {Louvain-la-Neuve (Belgium)},
      publisher    = {UCL},
      reportid     = {FZJ-2013-01314},
      pages        = {181 p.},
      year         = {2012},
      note         = {Université catholique de Louvain (Belgium), Diss., 2012},
      abstract     = {Soil water content is widely recognized as a key component
                      of the water, energy and carbon cycles and knowledge of its
                      spatiotemporal distribution is in particular needed for
                      developing optimal and sustainable environmental and
                      agricultural management strategies. In that context, we
                      analyzed and further developed advanced groundpenetrating
                      radar (GPR) and microwave radiometry techniques for
                      high-resolution mapping and monitoring of shallow soil water
                      content at the field scale. First, far-field ultra-wideband
                      GPR and L-band radiometer were used for mapping soil water
                      content over two test sites with bare soils and the results
                      were compared to reference ground truths. For GPR, soil
                      water content was derived from full-wave inversion focusing
                      on the surface reflection while for radiometer a radiative
                      transfer model was used. Both techniques provided relatively
                      good results, especially for reconstructing spatial moisture
                      patterns in relation to topography and forced conditions
                      (differential irrigation and soil tilth). Nevertheless,
                      absolute estimates were subject to inherent discrepancies
                      that were attributed to the different characterization
                      scales and local variability. Second, we addressed the
                      roughness modeling problem. For GPR, we combined the
                      full-wave GPR model with a roughness model derived from the
                      Kirchhoff scattering theory. Laboratory experiments showed
                      that this approach performs well for roughness amplitudes
                      reaching up to one fourth the wavelength. For the
                      radiometer, we used an empirical equation which requires
                      calibrating ground truths. This approach was successfully
                      validated in field conditions. Finally, GPR and radiometer
                      measurements were performed over a sand box subject to
                      hydrostatic equilibrium with a range of water table depths.
                      For each technique, all measurements were aggregated in an
                      inversion scheme to reconstruct the vertical water content
                      profiles, which were constrained using the van Genuchten
                      water retention equation. The results were in close
                      agreement with reference timedomain reflectometry
                      measurements. Our results open promising research and
                      application perspectives for the joint use of active and
                      passive microwave remote sensing for soil moisture
                      retrieval. In that respect, we addressed new avenues for
                      characterizing crop canopies and water-stress related
                      phenomena.},
      keywords     = {Dissertation (GND)},
      cin          = {IBG-3},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {246 - Modelling and Monitoring Terrestrial Systems: Methods
                      and Technologies (POF2-246)},
      pid          = {G:(DE-HGF)POF2-246},
      typ          = {PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/132075},
}