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@ARTICLE{Pisek:901828,
      author       = {Pisek, Jan and Erb, Angela and Korhonen, Lauri and
                      Biermann, Tobias and Carrara, Arnaud and Cremonese, Edoardo
                      and Cuntz, Matthias and Fares, Silvano and Gerosa, Giacomo
                      and Grünwald, Thomas and Hase, Niklas and Heliasz, Michal
                      and Ibrom, Andreas and Knohl, Alexander and Kobler, Johannes
                      and Kruijt, Bart and Lange, Holger and Leppänen, Leena and
                      Limousin, Jean-Marc and Serrano, Francisco Ramon Lopez and
                      Loustau, Denis and Lukeš, Petr and Lundin, Lars and
                      Marzuoli, Riccardo and Mölder, Meelis and Montagnani,
                      Leonardo and Neirynck, Johan and Peichl, Matthias and
                      Rebmann, Corinna and Rubio, Eva and Santos-Reis, Margarida
                      and Schaaf, Crystal and Schmidt, Marius and Simioni,
                      Guillaume and Soudani, Kamel and Vincke, Caroline},
      title        = {{R}etrieval and validation of forest background
                      reflectivity from daily {M}oderate {R}esolution {I}maging
                      {S}pectroradiometer ({MODIS}) bidirectional reflectance
                      distribution function ({BRDF}) data across {E}uropean
                      forests},
      journal      = {Biogeosciences},
      volume       = {18},
      number       = {2},
      issn         = {1726-4189},
      address      = {Katlenburg-Lindau [u.a.]},
      publisher    = {Copernicus},
      reportid     = {FZJ-2021-03851},
      pages        = {621 - 635},
      year         = {2021},
      abstract     = {Information about forest background reflectance is needed
                      for accurate biophysical parameter retrieval from forest
                      canopies (overstory) with remote sensing. Separating under-
                      and overstory signals would enable more accurate modeling of
                      forest carbon and energy fluxes. We retrieved values of the
                      normalized difference vegetation index (NDVI) of the forest
                      understory with the multi-angular Moderate Resolution
                      Imaging Spectroradiometer (MODIS) bidirectional reflectance
                      distribution function (BRDF)/albedo data (gridded 500 m
                      daily Collection 6 product), using a method originally
                      developed for boreal forests. The forest floor background
                      reflectance estimates from the MODIS data were compared with
                      in situ understory reflectance measurements carried out at
                      an extensive set of forest ecosystem experimental sites
                      across Europe. The reflectance estimates from MODIS data
                      were, hence, tested across diverse forest conditions and
                      phenological phases during the growing season to examine
                      their applicability for ecosystems other than boreal
                      forests. Here we report that the method can deliver good
                      retrievals, especially over different forest types with open
                      canopies (low foliage cover). The performance of the method
                      was found to be limited over forests with closed canopies
                      (high foliage cover), where the signal from understory
                      becomes too attenuated. The spatial heterogeneity of
                      individual field sites and the limitations and documented
                      quality of the MODIS BRDF product are shown to be important
                      for the correct assessment and validation of the retrievals
                      obtained with remote sensing.},
      cin          = {IBG-3},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {2173 - Agro-biogeosystems: controls, feedbacks and impact
                      (POF4-217)},
      pid          = {G:(DE-HGF)POF4-2173},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000613959500003},
      doi          = {10.5194/bg-18-621-2021},
      url          = {https://juser.fz-juelich.de/record/901828},
}