EUMETSAT’S LSA-SAF EVAPOTRANSPIRATION: COMPARISONS OF OPERATIONAL PRODUCT TO OBSERVATIONS AND MODELS AT HYDROLOGICAL BASINS SCALE

nstantaneous and daily evapotranspiration (ET) products developed in the framework of EUMETSAT‟ s Satellite Application Facility on Land Surface Analysis (LSA-SAF) are based on a physical approach in which data derived from Meteosat Second Generation (MSG) satellites together with land-cover information are used to constrain a physical model of energy exchange between the soil-vegetation system and the atmosphere. A first algorithm generates, in near-real time, an instantaneous evapotranspiration estimate (MET) over four regions defined in the MSG FOV (Europe, Africa and the west of South America) with MSG spatial resolution (3 km at sub satellite point) and a temporal time step of 30 minutes. Once all instantaneous ET estimates for a given day have been generated, a second algorithm integrates these values and generates a daily-integrated product (DMET). The MET product has been validated mainly over Europe given that over remaining regions (Africa and South America), reference data for validation is very scarce and the validation has been accomplished mainly by models inter-comparison and comparison to local observations over a few locations. The MET and DMET products have been declared operational in November 2010 and since then, instantaneous and daily ET products are disseminated to interested users through LSA-SAF system ( http://landsaf. meteo. pt/) and via EUMETCAST.