Uncertainties on evapotranspiration derived from landsat images depending on reliability of albedo input data over a mediterranean agricultural region

Evapotranspiration (ET) accounts for a dominant part of the hydrological cycle. Globally, nearly two-thirds of precipitations over land are returned back to the atmosphere by ET. This proportion may be higher in dry areas, such as the Mediterranean basin. ET is difficult to assess in space and time because it depends on the water status and the energy processes at the Earth surface, which are highly variable. The work presented here aimed to quantify uncertainties in ET estimations from multispectral data from Landsat-7/ETM+ over a Mediterranean agricultural region depending on input data accuracy. Particular emphasis is given to albedo estimation, 12 different models being tested. Continuous ground measurements of albedo and net radiation were available for the period 2007 to 2010 for different surfaces. According to the reliability of albedo estimation from Landsat-7 data, it is possible to retrieve latent heat flux estimates with an uncertainty around 10 W·m-2.