Conclusions

Processes involved in this study were related to the heat transfer at the land-atmosphere interface in an Alpine watershed. Surface characteristics, such as topography and type of land cover, and surface processes, such as incoming and outgoing fluxes, represented the focus of our attention in space and time observation and modelling strategy.

A complete procedure based on a single layer model has been described from space-based and ground-based measurements to the modelled heat and mass transfer exchange fluxes at the surface-atmosphere interface.

Input parameters to the energy balance model were spatially distributed at the catchment scale with a grid cell defined by the pixel size of remotely-sensed data. Biogeophysical parameters, such as outgoing short-wave and long-wave radiation, derived from satellite observations are naturally spatially distributed, while parameters derived from ground observations were distributed using the information of the DEM. Digital elevation data were essential to accurately correct the radiometric signal recorded by the satellite sensor.

Watershed stratification, derived from classification of satellite imagery, allowed to manage other parameters characteristic of the surfaces, such as roughness length and emissivity. Fractional cover served to properly define albedo and emissivity for mixed pixels.

Daily evapotranspiration estimates given by the model were in better agreement with estimates computed using the Priestley-Taylor method rather than that of Penman-Monteith.

Although remotely-sensed data proved their ability in determining variables and parameters, such as vegetation structure information and optical and thermal properties of soil and vegetation for driving SVAT models, further efforts are needed to analyse errors induced by uncertainties in remotely-sensed and meteorological forcing variables, as well as to determine the possible recurrence of space measurements by combining data from different sensors.

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