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@ARTICLE{Graf:151964,
      author       = {Graf, Alexander and Boer, Anneke and Moene, Arnold and
                      Vereecken, Harry},
      title        = {{I}ntercomparison of {M}ethods for the {S}imultaneous
                      {E}stimation of {Z}ero-{P}lane {D}isplacement and
                      {A}erodynamic {R}oughness {L}ength from {S}ingle-{L}evel
                      {E}ddy-{C}ovariance {D}ata},
      journal      = {Boundary layer meteorology},
      volume       = {151},
      number       = {2},
      issn         = {1573-1472},
      address      = {Dordrecht [u.a.]},
      publisher    = {Springer Science + Business Media B.V},
      reportid     = {FZJ-2014-01796},
      pages        = {373 - 387},
      year         = {2014},
      abstract     = {We applied three approaches to estimate the zero-plane
                      displacement d through the aerodynamic measurement height z
                      (with z = zm − d and zm being the measurement height above
                      the surface), and the aerodynamic roughness length z0, from
                      single-level eddy covariance data. Two approaches (one
                      iterative and one regression-based) were based on the
                      universal function in the logarithmic wind profile and
                      yielded an inherently simultaneous estimation of both d and
                      z0. The third approach was based on flux-variance
                      similarity, where estimation of d and consecutive estimation
                      of z0 are independent steps. Each approach was further
                      divided into two methods differing either with respect to
                      the solution technique (profile approaches) or with respect
                      to the variable (variance of vertical wind and temperature,
                      respectively). All methods were applied to measurements
                      above a large, growing wheat field where a uniform canopy
                      height and its frequent monitoring provided plausibility
                      limits for the resulting estimates of time-variant d and z0.
                      After applying, for each approach, a specific data filtering
                      that accounted for the range of conditions (e.g. stability)
                      for which it is valid, five of the six methods were able to
                      describe the temporal changes of roughness parameters
                      associated with crop growth and harvest, and four of them
                      agreed on d to within 0.3 m most of the time. Application of
                      the same methods to measurements with a more heterogeneous
                      footprint consisting of fully-grown sugarbeet and a varying
                      contribution of adjacent harvested fields exhibited a
                      plausible dependence of the roughness parameters on
                      sugarbeet fraction. It also revealed that the methods
                      producing the largest outliers can differ between site
                      conditions and stability. We therefore conclude that when
                      determining d for canopies with unknown properties from
                      single-level measurements, as is increasingly done, it is
                      important to compare the results of a number of methods
                      rather than rely on a single one. An ensemble average or
                      median of the results, possibly after elimination of methods
                      that produce outliers, can help to yield more robust
                      estimates. The estimates of z0 were almost exclusively
                      physically plausible, although d was considered unknown and
                      estimated simultaneously with the methods and results
                      described above.},
      cin          = {IBG-3},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {255 - Terrestrial Systems: From Observation to Prediction
                      (POF3-255) / DFG project 139819005 - Links between local
                      scale and catchment scale measurements and modelling of gas
                      exchange processes over land surfaces (139819005) / DFG
                      project 15232683 - TRR 32: Muster und Strukturen in
                      Boden-Pflanzen-Atmosphären-Systemen: Erfassung,
                      Modellierung und Datenassimilation (15232683)},
      pid          = {G:(DE-HGF)POF3-255 / G:(GEPRIS)139819005 /
                      G:(GEPRIS)15232683},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000333334600010},
      doi          = {10.1007/s10546-013-9905-z},
      url          = {https://juser.fz-juelich.de/record/151964},
}