A SIMPLE METHOD FOR ESTIMATING REGIONAL EVAPOTRANSPIRATION FROM INFRARED SURFACE-TEMPERATURE DATA

A new method aimed at estimating regional evapotranspiration throughout the day from a single measurement of surface temperature, such as a temperature derived from satellite data is presented. This method is based on the coupling of a simple surface exchange model with a simple planetary boundary layer model. The only required surface parameters are the albedo, emissivity and roughness length, provided that the structure parameters of the boundary layer can be inferred from radio soundings. Radiation fluxes have to be known but the usual climatic data, such as wind speed, air temperature and vapour pressure, are calculated by the model. The method is validated against three sets of micrometeorological data obtained under various conditions above short plant canopies. The applicability and limitations of this model are discussed.