Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 6, issue 8
Biogeosciences, 6, 1389–1404, 2009
https://doi.org/10.5194/bg-6-1389-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.
Biogeosciences, 6, 1389–1404, 2009
https://doi.org/10.5194/bg-6-1389-2009
© Author(s) 2009. This work is distributed under
the Creative Commons Attribution 3.0 License.

  05 Aug 2009

05 Aug 2009

Modelling LAI at a regional scale with ISBA-A-gs: comparison with satellite-derived LAI over southwestern France

A. Brut1,*, C. Rüdiger1,**, S. Lafont1,2, J.-L. Roujean1, J.-C. Calvet1, L. Jarlan1,*, A.-L. Gibelin1, C. Albergel1, P. Le Moigne1, J.-F. Soussana3, K. Klumpp3, D. Guyon4, J.-P. Wigneron4, and E. Ceschia5 A. Brut et al.
  • 1CNRM/GAME (Météo-France, CNRS), Toulouse, France
  • 2LSCE (CEA, CNRS), Gif-sur-Yvette, France
  • 3Unité de Recherche sur l'Ecosystème Prairial (INRA), Clermont-Ferrand, France
  • 4Unité de recherche Ecologie fonctionnelle et Physique de l'Environnement (INRA), Villenave d'Ornon, France
  • 5CESBIO (UPS, CNRS, IRD, CNES), Toulouse, France
  • *now at: CESBIO (UPS, CNRS, IRD, CNES), Toulouse, France
  • **now at: Department of Civil and Environmental Engineering, The University of Melbourne, Melbourne, Australia

Abstract. A CO2-responsive land surface model (the ISBA-A-gs model of Météo-France) is used to simulate photosynthesis and Leaf Area Index (LAI) in southwestern France for a 3-year period (2001–2003). A domain of about 170 000 km2 is covered at a spatial resolution of 8 km. The capability of ISBA-A-gs to reproduce the seasonal and the interannual variability of LAI at a regional scale, is assessed with satellite-derived LAI products. One originates from the CYCLOPES programme using SPOT/VEGETATION data, and two products are based on MODIS data. The comparison reveals discrepancies between the satellite LAI estimates and between satellite and simulated LAI values, both in their intensity and in the timing of the leaf onset. The model simulates higher LAI values for the C3 crops than the satellite observations, which may be due to a saturation effect within the satellite signal or to uncertainties in model parameters. The simulated leaf onset presents a significant delay for C3 crops and mountainous grasslands. In-situ observations at a mid-altitude grassland site show that the generic temperature response of photosynthesis used in the model is not appropriate for plants adapted to the cold climatic conditions of the mountainous areas. This study demonstrates the potential of LAI remote sensing products for identifying and locating models' shortcomings at a regional scale.

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