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@ARTICLE{Iwema:203402,
      author       = {Iwema, J. and Rosolem, R. and Baatz, R. and Wagener, T. and
                      Bogena, Heye},
      title        = {{I}nvestigating temporal field sampling strategies for
                      site-specific calibration of three soil moisture–neutron
                      intensity parameterisation methods},
      journal      = {Hydrology and earth system sciences},
      volume       = {19},
      number       = {7},
      issn         = {1607-7938},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2015-05345},
      pages        = {3203 - 3216},
      year         = {2015},
      abstract     = {The Cosmic-Ray Neutron Sensor (CRNS) can provide soil
                      moisture information at scales relevant to
                      hydrometeorological modelling applications. Site-specific
                      calibration is needed to translate CRNS neutron intensities
                      into sensor footprint average soil moisture contents. We
                      investigated temporal sampling strategies for calibration of
                      three CRNS parameterisations (modified N0, HMF, and COSMIC)
                      by assessing the effects of the number of sampling days and
                      soil wetness conditions on the performance of the
                      calibration results while investigating actual neutron
                      intensity measurements, for three sites with distinct
                      climate and land use: a semi-arid site, a temperate
                      grassland, and a temperate forest. When calibrated with 1
                      year of data, both COSMIC and the modified N0 method
                      performed better than HMF. The performance of COSMIC was
                      remarkably good at the semi-arid site in the USA, while the
                      N0mod performed best at the two temperate sites in Germany.
                      The successful performance of COSMIC at all three sites can
                      be attributed to the benefits of explicitly resolving
                      individual soil layers (which is not accounted for in the
                      other two parameterisations). To better calibrate these
                      parameterisations, we recommend in situ soil sampled to be
                      collected on more than a single day. However, little
                      improvement is observed for sampling on more than 6 days. At
                      the semi-arid site, the N0mod method was calibrated better
                      under site-specific average wetness conditions, whereas HMF
                      and COSMIC were calibrated better under drier conditions.
                      Average soil wetness condition gave better calibration
                      results at the two humid sites. The calibration results for
                      the HMF method were better when calibrated with combinations
                      of days with similar soil wetness conditions, opposed to
                      N0mod and COSMIC, which profited from using days with
                      distinct wetness conditions. Errors in actual neutron
                      intensities were translated to average errors specifically
                      to each site. At the semi-arid site, these errors were below
                      the typical measurement uncertainties from in situ
                      point-scale sensors and satellite remote sensing products.
                      Nevertheless, at the two humid sites, reduction in
                      uncertainty with increasing sampling days only reached
                      typical errors associated with satellite remote sensing
                      products. The outcomes of this study can be used by
                      researchers as a CRNS calibration strategy guideline.},
      cin          = {IBG-3},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {255 - Terrestrial Systems: From Observation to Prediction
                      (POF3-255)},
      pid          = {G:(DE-HGF)POF3-255},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000358918200013},
      doi          = {10.5194/hess-19-3203-2015},
      url          = {https://juser.fz-juelich.de/record/203402},
}