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@ARTICLE{Andreasen:829872,
      author       = {Andreasen, Mie and Jensen, Karsten H. and Desilets, Darin
                      and Zreda, Marek and Bogena, Heye and Looms, Majken C.},
      title        = {{C}osmic-ray neutron transport at a forest field site: the
                      sensitivity to various environmental conditions with focus
                      on biomass and canopy interception},
      journal      = {Hydrology and earth system sciences},
      volume       = {21},
      number       = {4},
      issn         = {1607-7938},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2017-03488},
      pages        = {1875 - 1894},
      year         = {2017},
      abstract     = {Cosmic-ray neutron intensity is inversely correlated to all
                      hydrogen present in the upper decimeters of the subsurface
                      and the first few hectometers of the atmosphere above the
                      ground surface. This correlation forms the base of the
                      cosmic-ray neutron soil moisture estimation method. The
                      method is, however, complicated by the fact that several
                      hydrogen pools other than soil moisture affect the neutron
                      intensity. In order to improve the cosmic-ray neutron soil
                      moisture estimation method and explore the potential for
                      additional applications, knowledge about the environmental
                      effect on cosmic-ray neutron intensity is essential (e.g.,
                      the effect of vegetation, litter layer and soil type). In
                      this study the environmental effect is examined by
                      performing a sensitivity analysis using neutron transport
                      modeling. We use a neutron transport model with various
                      representations of the forest and different parameters
                      describing the subsurface to match measured height profiles
                      and time series of thermal and epithermal neutron
                      intensities at a field site in Denmark. Overall, modeled
                      thermal and epithermal neutron intensities are in
                      satisfactory agreement with measurements; however, the
                      choice of forest canopy conceptualization is found to be
                      significant. Modeling results show that the effect of canopy
                      interception, soil chemistry and dry bulk density of litter
                      and mineral soil on neutron intensity is small. On the other
                      hand, the neutron intensity decreases significantly with
                      added litter-layer thickness, especially for epithermal
                      neutron energies. Forest biomass also has a significant
                      influence on the neutron intensity height profiles at the
                      examined field site, altering both the shape of the profiles
                      and the ground-level thermal-to-epithermal neutron ratio.
                      This ratio increases with increasing amounts of biomass, and
                      was confirmed by measurements from three sites representing
                      agricultural, heathland and forest land cover. A much
                      smaller effect of canopy interception on the ground-level
                      thermal-to-epithermal neutron ratio was modeled. Overall,
                      the results suggest a potential to use ground-level
                      thermal-to-epithermal neutron ratios to discriminate the
                      effect of different hydrogen contributions on the neutron
                      signal.},
      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:000398973900001},
      doi          = {10.5194/hess-21-1875-2017},
      url          = {https://juser.fz-juelich.de/record/829872},
}