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@ARTICLE{Rtzer:155913,
      author       = {Rötzer, Kathrina and Montzka, Carsten and Bogena, Heye and
                      Wagner, W. and Kerr, Y. H. and Kidd, R. and Vereecken,
                      Harry},
      title        = {{C}atchment scale validation of {SMOS} and {ASCAT} soil
                      moisture products using hydrological modeling and temporal
                      stability analysis},
      journal      = {Journal of hydrology},
      volume       = {519},
      number       = {Part A},
      issn         = {0022-1694},
      address      = {Amsterdam [u.a.]},
      publisher    = {Elsevier},
      reportid     = {FZJ-2014-04843},
      pages        = {934 - 946},
      year         = {2014},
      abstract     = {Since soil moisture is an important influencing factor of
                      the hydrological cycle, knowledge of its spatio- temporal
                      dynamics is crucial for climate and hydrological modeling.
                      In recent years several soil moisture data products from
                      satellite information have become available with global
                      coverage and sub-monthly resolution. Since the remote
                      sensing of soil moisture is an indirect measurement method
                      and influenced by a large number of factors (e.g.
                      atmospheric correction, vegetation, soil roughness etc.), a
                      comprehensive validation of the resulting soil moisture
                      products is required. However, the coarse spatial resolution
                      of these products hampers the comparison with point-scale in
                      situ measurements. Therefore, upscaling of in situ to the
                      scale of the satellite data is needed. We present the
                      validation results of the soil moisture products of the
                      years 2010 to 2012 retrieved from the Soil Moisture and
                      Ocean Salinity (SMOS) and the Advanced Scatterometer (ASCAT)
                      for the Rur and Erft catchments in western Germany. For the
                      upscaling of in situ data obtained from three test sites of
                      the Terrestrial Environmental Observatories (TERENO)
                      initiative we used the hydrological model WaSiM ETH.
                      Correlation of the SMOS product to modeled and upscaled soil
                      moisture resulted in a mean correlation coefficient of 0.28
                      whereas for ASCAT a correlation coefficient of 0.50 was
                      obtained. However, for specific regions the SMOS product
                      showed similar correlation coefficients as the ASCAT
                      product. While for ASCAT correlation was mainly dependent on
                      topography and vegetation, SMOS was also influenced by
                      radiofrequency interferences in our study area. Both
                      products show dry biases as compared to the soil moisture
                      reference. However, while SMOS showed relatively constant
                      bias values, ASCAT bias is variable throughout the year. As
                      an additional validation method we performed a temporal
                      stability analysis of the retrieved spatio-temporal soil
                      moisture data. Through investigation of mean relative
                      differences of soil moisture for every pixel, their standard
                      deviations and their rankings, we analyzed the temporal
                      persistence of spatial patterns. Our results show high
                      standard deviations for both SMOS and ASCAT soil moisture
                      products as compared to modeled soil moisture, indicating a
                      lower temporal persistence. The consistence of ranks of mean
                      relative differences was low for SMOS and relative ASCAT
                      soil moisture compared to modeled soil moisture, while ASCAT
                      soil moisture, converted to absolute values, showed higher
                      rank consistence.},
      cin          = {IBG-3},
      ddc          = {690},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {246 - Modelling and Monitoring Terrestrial Systems: Methods
                      and Technologies (POF2-246) / 255 - Terrestrial Systems:
                      From Observation to Prediction (POF3-255)},
      pid          = {G:(DE-HGF)POF2-246 / G:(DE-HGF)POF3-255},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000347589500079},
      doi          = {10.1016/j.jhydrol.2014.07.065},
      url          = {https://juser.fz-juelich.de/record/155913},
}