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@ARTICLE{Jagdhuber:890906,
      author       = {Jagdhuber, Thomas and Montzka, Carsten and Lopez-Martinez,
                      Carlos and Baur, Martin J. and Link, Moritz and Piles, Maria
                      and Das, Narendra Narayan and Jonard, Francois},
      title        = {{E}stimation of {V}egetation {S}tructure {P}arameters
                      {F}rom {SMAP} {R}adar {I}ntensity {O}bservations},
      journal      = {IEEE transactions on geoscience and remote sensing},
      volume       = {59},
      number       = {1},
      issn         = {1558-0644},
      address      = {New York, NY},
      publisher    = {IEEE78494},
      reportid     = {FZJ-2021-01237},
      pages        = {151-167},
      year         = {2021},
      abstract     = {In this article, we present a multipolarimetric estimation
                      approach for two model-based vegetation structure parameters
                      (shape A and orientation distribution ψ of the main canopy
                      elements). The approach is based on a reduced observation
                      set of three incoherent (no phase information) polarimetric
                      backscatter intensities (|S HH | 2 , |S HV | 2 , and |S VV |
                      2 ) combined with a two-parameter (A P and ψ) discrete
                      scatterer model of vegetation. The objective is to
                      understand whether this confined set of observations
                      contains enough information to estimate the two vegetation
                      structure parameters from the L-band radar signals. In order
                      to disentangle soil and vegetation scattering influences on
                      these signals and ultimately perform a vegetation only
                      retrieval of vegetation shape A and orientation distribution
                      ψ, we use the subpixel spatial heterogeneity expressed by
                      the covariation of co- and cross-polarized backscatter Γ
                      PP-PQ of the neighboring cells and assume it is indicative
                      for the amount of a vegetation-only co-to-cross-polarized
                      backscatter ratio μ PP-PQ . The ratio-based retrieval
                      approach enables a relative (no absolute backscatter)
                      estimation of the vegetation structure parameters which is
                      more robust compared to retrievals with absolute terms. The
                      application of the developed algorithm on global L-band Soil
                      Moisture Active Passive (SMAP) radar data acquired from
                      April to July 2015 indicates the potential and limitations
                      of estimating these two parameters when no fully
                      polarimetric data are available. A focus study on six
                      different regions of interest, spanning land cover from
                      barren land to tropical rainforest, shows a steady increase
                      in orientation distribution toward randomly oriented volumes
                      and a continuous decrease in shape arriving at dipoles for
                      tropical vegetation. A comparison with independent data sets
                      of vegetation height and above-ground biomass confirms this
                      consistent and meaningful retrieval of A P and ψ.},
      cin          = {IBG-3},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {217 - Für eine nachhaltige Bio-Ökonomie – von
                      Ressourcen zu Produkten (POF4-217)},
      pid          = {G:(DE-HGF)POF4-217},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000603079000012},
      doi          = {10.1109/TGRS.2020.2991252},
      url          = {https://juser.fz-juelich.de/record/890906},
}