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MODELISATION DES CHANGEMENTS D'ECHELLE ET PRISE EN COMPTE DES HETEROGENEITES DE SURFACE ET DE LEUR VARIABILITE SPATIALE DANS LES INTERACTIONS
SOL-VEGETATION-ATMOSPHERE

Abstract : This study presents and evaluates a few methodologies for scaling the water and energy balance processes at the surface of the continents. The main objectives are i) to evaluate the impact of partial surface vegetation cover and surface parameters variability on the Soil-Vegetation-Atmosphere Transfer (SVAT) modelling and ii) to introduce some scaling methods to link the model formalism and parameters between the point scale and the regional scale (upscaling). We first tried to find the appropriate representation of patchy vegetated surface functioning (small-scale heterogeneity). Partially vegetated surfaces are classically described by “dual source” SVAT models where standing vegetation and the underlying substrate are organised the one above the other. This proves to be unrealistic when large fractions of bare soil interact directly with the atmosphere. We investigated the threshold value of a roughness index for which the substrate and the vegetation have to be described as a “mosaic”, i.e. side by side. On a larger scale, a Statistical Analysis has been performed to evaluate the impact of parameter variability on the seasonal and annual water balance for a medium size water catchment located in Australia. Aggregation rules aiming at deriving effective parameters representative of the regional scale have been verified or invalidated. Then the one-dimensional representation of the SiSPAT (Simple Soil Vegetation Atmosphere Transfer) SVAT model has been extended with the help of a stochastic and a deterministic distributions and compared with equivalent hydrological representations. As an alternative to the complexity of the SiSPAT SVAT model, a simple parameterisation of the main land surface processes has been developed and partially evaluated. This analytical scheme holds some promise for scaling applications.
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https://tel.archives-ouvertes.fr/tel-00172979
Contributor : Gilles Boulet <>
Submitted on : Tuesday, September 18, 2007 - 3:39:07 PM
Last modification on : Thursday, November 19, 2020 - 3:54:29 PM
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Gilles Boulet. MODELISATION DES CHANGEMENTS D'ECHELLE ET PRISE EN COMPTE DES HETEROGENEITES DE SURFACE ET DE LEUR VARIABILITE SPATIALE DANS LES INTERACTIONS
SOL-VEGETATION-ATMOSPHERE. Hydrologie. Université Joseph-Fourier - Grenoble I; CNRS; IRD; Institut National Polytechnique de Grenoble - INPG, 1999. Français. ⟨tel-00172979⟩

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