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@ARTICLE{Klosterhalfen:857929,
      author       = {Klosterhalfen, Anne and Moene, A. F. and Schmidt, Marius
                      and Scanlon, T. M. and Vereecken, Harry and Graf, Alexander},
      title        = {{S}ensitivity analysis of a source partitioning method for
                      {H}$_2${O} and {CO}$_2$ fluxes based on high frequency eddy
                      covariance data: {F}indings from field data and large eddy
                      simulations},
      journal      = {Agricultural and forest meteorology},
      volume       = {265},
      issn         = {0168-1923},
      address      = {Amsterdam [u.a.]},
      publisher    = {Elsevier},
      reportid     = {FZJ-2018-06883},
      pages        = {152 - 170},
      year         = {2019},
      note         = {Netherlands Science Foundation under contract NWO 15774},
      abstract     = {Scanlon and Sahu (2008) and Scanlon and Kustas (2010)
                      proposed a source partitioning method (SK10 in the
                      following) to estimate contributions of transpiration,
                      evaporation, photosynthesis, and respiration to H$_2$O and
                      CO$_2$ fluxes obtained by the eddy covariance method. High
                      frequency eddy covariance raw data time series are needed,
                      and the source partitioning is estimated based on separate
                      application of the flux-variance similarity theory to
                      stomatal and non-stomatal components of the regarded fluxes,
                      as well as on additional assumptions on leaf-level water use
                      efficiency (WUE).\\We applied SK10 to data from two test
                      sites (forest and cropland) and analyzed partitioning
                      results depending on various ways to estimate WUE from
                      available data. Also, we conducted large eddy simulations
                      (LES), simulating the turbulent transport of H$_2$O and
                      CO$_2$ for contrasting vertical distributions of the canopy
                      sinks/sources, as well as for varying relative magnitudes of
                      soil sources and canopy sinks/sources. SK10 was applied to
                      the synthetic high frequency data generated by LES and the
                      effects of canopy type, measurement height, given
                      sink-source-distributions, and input of varying WUEs were
                      tested regarding the partitioning performance. SK10 requires
                      that the correlation coefficient between stomatal and
                      non-stomatal scalar fluctuations is determined by the ratio
                      of the transfer efficiencies of these scalar components, an
                      assumption (transfer assumption in the following) that could
                      be tested with the generated LES data.\\The partitioning
                      results of the field sites yielded satisfactory flux
                      fractions, when fair-weather conditions (no precipitation)
                      and a high productive state of the vegetation were present.
                      Further, partitioning performance with regard to soil fluxes
                      increased with crop maturity. Results also showed relatively
                      large dependencies on WUE, where the partitioning factors
                      (median) changed by around -57\% and +36\%. Measurements of
                      outgoing longwave radiation used for the estimation of
                      foliage temperature and WUE could slightly increase the
                      plausibility of the partitioning results in comparison to
                      soil respiration measurements by decreasing the partitioning
                      factor by up to 42\%. The LES-based analysis revealed that
                      for a satisfying performance of SK10, a certain degree of
                      decorrelation of the H$_2$O and CO$_2$ fluctuations (here,
                      |ρ$_{q’c’}$| < 0.975) was needed. This decorrelation is
                      enhanced by a clear separation between soil sources and
                      canopy sinks/sources, and for observations within the
                      roughness sublayer. The expected dependence of the
                      partitioning results on the WUE input could be observed.
                      However, due to violation of the abovementioned transfer
                      assumption, the known true input WUE did not yield the known
                      true input partitioning. This could only be achieved after
                      introducing correction factors for the transfer assumption,
                      which were known however only in the special case of the LES
                      experiments.},
      cin          = {IBG-3},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {255 - Terrestrial Systems: From Observation to Prediction
                      (POF3-255) / IDAS-GHG - Instrumental and Data-driven
                      Approaches to Source-Partitioning of Greenhouse Gas Fluxes:
                      Comparison, Combination, Advancement (BMBF-01LN1313A)},
      pid          = {G:(DE-HGF)POF3-255 / G:(DE-Juel1)BMBF-01LN1313A},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000456751200014},
      doi          = {10.1016/j.agrformet.2018.11.003},
      url          = {https://juser.fz-juelich.de/record/857929},
}