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Hydrology and Earth System Sciences An interactive open-access journal of the European Geosciences Union
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Volume 13, issue 7
Hydrol. Earth Syst. Sci., 13, 1337–1347, 2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Advances in land surface hydrological processes – field...

Hydrol. Earth Syst. Sci., 13, 1337–1347, 2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

  29 Jul 2009

29 Jul 2009

Evaluation of the Surface Energy Balance System (SEBS) applied to ASTER imagery with flux-measurements at the SPARC 2004 site (Barrax, Spain)

J. van der Kwast1,*, W. Timmermans2, A. Gieske2, Z. Su2, A. Olioso3, L. Jia4, J. Elbers4, D. Karssenberg1, and S. de Jong1 J. van der Kwast et al.
  • 1Department of Physical Geography, Faculty of Geosciences, Utrecht University, Utrecht, The Netherlands
  • 2International Inst. for Geo-Information Science and Earth Observation (ITC), Enschede, The Netherlands
  • 3Institut national de la recherche agronomique (INRA), Avignon, France
  • 4Alterra, Wageningen University and Research Centre, Wageningen, The Netherlands
  • *now at: Flemish Institute for Technological Research (VITO), Mol, Belgium

Abstract. Accurate quantification of the amount and spatial variation of evapotranspiration is important in a wide range of disciplines. Remote sensing based surface energy balance models have been developed to estimate turbulent surface energy fluxes at different scales. The objective of this study is to evaluate the Surface Energy Balance System (SEBS) model on a landscape scale, using tower-based flux measurements at different land cover units during an overpass of the ASTER sensor over the SPARC 2004 experimental site in Barrax (Spain). A sensitivity analysis has been performed in order to investigate to which variable the sensible heat flux is most sensitive. Taking into account their estimation errors, the aerodynamic parameters (hc, z0M and d0) can cause large deviations in the modelling of sensible heat flux. The effect of replacement of empirical derivation of these aerodynamic parameters in the model by field estimates or literature values is investigated by testing two scenarios: the Empirical Scenario in which empirical equations are used to derive aerodynamic parameters and the Field Scenario in which values from field measurements or literature are used to replace the empirical calculations of the Empirical Scenario. In the case of a homogeneous land cover in the footprints of the measurements, the Field Scenario only resulted in a small improvement, compared to the Empirical Scenario. The Field Scenario can even worsen the result in the case of heterogeneous footprints, by creating sharp borders related to the land cover map. In both scenarios modelled fluxes correspond better with flux measurements over uniform land cover compared to cases where different land covers are mixed in the measurement footprint. Furthermore SEBS underestimates sensible heat flux especially over dry and sparsely vegetated areas, which is common in single-source models.

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