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@ARTICLE{Hoppe:202191,
      author       = {Hoppe, Charlotte and Elbern, H. and Schwinger, J.},
      title        = {{A} variational data assimilation system for
                      soil–atmosphere flux estimates for the {C}ommunity {L}and
                      {M}odel ({CLM}3.5)},
      journal      = {Geoscientific model development},
      volume       = {7},
      number       = {3},
      issn         = {1991-9603},
      address      = {Katlenburg-Lindau},
      publisher    = {Copernicus},
      reportid     = {FZJ-2015-04480},
      pages        = {1025 - 1036},
      year         = {2014},
      abstract     = {This paper presents the development and implementation of a
                      spatio-temporal variational data assimilation system
                      (4D-var) for the soil–vegetation–atmosphere transfer
                      model "Community Land Model" (CLM3.5), along with the
                      development of the adjoint code for the core
                      soil–atmosphere transfer scheme of energy and soil
                      moisture. The purpose of this work is to obtain an improved
                      estimation technique for the energy fluxes (sensible and
                      latent heat fluxes) between the soil and the atmosphere.
                      Optimal assessments of these fluxes are neither available
                      from model simulations nor measurements alone, while a
                      4D-var data assimilation has the potential to combine both
                      information sources by a Best Linear Unbiased Estimate
                      (BLUE). The 4D-var method requires the development of the
                      adjoint model of the CLM which is established in this work.
                      The new data assimilation algorithm is able to assimilate
                      soil temperature and soil moisture measurements for
                      one-dimensional columns of the model grid. Numerical
                      experiments were first used to test the algorithm under
                      idealised conditions. It was found that the analysis
                      delivers improved results whenever there is a dependence
                      between the initial values and the assimilated quantity.
                      Furthermore, soil temperature and soil moisture from in situ
                      field measurements were assimilated. These calculations
                      demonstrate the improved performance of flux estimates,
                      whenever soil property parameters are available of
                      sufficient quality. Misspecifications could also be
                      identified by the performance of the variational scheme.},
      cin          = {IEK-8},
      ddc          = {910},
      cid          = {I:(DE-Juel1)IEK-8-20101013},
      pnm          = {233 - Trace gas and aerosol processes in the troposphere
                      (POF2-233)},
      pid          = {G:(DE-HGF)POF2-233},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000341600100017},
      doi          = {10.5194/gmd-7-1025-2014},
      url          = {https://juser.fz-juelich.de/record/202191},
}