Evaporation for maritime catchment combining a meteorological model with vegetation information and airborne surface temperatures

Estimation of daily fluxes at regional scale using thermal infrared data through semi-empirical models is problematic under oceanic climates, due to the frequency of cloudy days and the subsequent low availability of thermal infrared images (TIR). The gap between available satellite information must therefore be bridged by simulation from cropwater balance models. in an experiment on a small agricultural catchment in Brittany (NW France) we have used TIR data and an agrometeorological model to estimate actual evapotranspiration (AET). The model is described: a new module has been added to take into account the canopy development through the LAI variations. Continuous micrometeorological measurements were made on three characteristic surfaces (meadow, wheal and stubble field). The agrometeorological model simulated correctly the main energy fluxes and the surface temperatures for these changing climatic conditions. Thermal images covering the whole catchment were acquired on 6 August 1993 using an airborne infrared camera. The comparison between the surface temperatures acquired by the camera and the ground measurements was satisfactory. We discussed the possibilities of combining these data with the model to estimate AET at the catchment scale.