Monitoring daily evapotranspiration at a regional scale from Landsat TM and ETM+ data: application to the Basilicata region

The increasing interest of hydrological, climatic and meteorological models in the different components of the surface energy balance has encouraged the development of operational methods for estimating surface energy fluxes at a regional scale. In this paper, a sequence of three high-resolution satellite-based surface energy fluxes images are analyzed over an extensive area with a large variety of land uses. Two images from Landsat 7-ETM+ (1999, 2002) and one from Landsat 5-TM (2004) are collected covering the whole Basilicata region (Southern Italy). A Simplified version of a Two-Source Energy Balance (STSEB) model is used to retrieve the surface sensible heat flux. A balance between the long-wave and short-wave radiation is applied to extract the net radiation flux. The evapotranspiration (LE) is obtained as a residual term of the energy balance equation. The different croplands are characterized from the CORINE Land Cover maps, and the required meteorological variables are obtained by interpolating the data of a network of agro-meteorological stations distributed within the region. Atmospheric profiles from radiosoundings are used in the radiative transfer model MODTRAN 4.0 to correct the satellite data. Maps of the different fluxes are produced. Daily LE results are compared with some ground measurements, and an analysis is made taking the land use classification as a basis. An accuracy close to 1 mm day-1 is obtained. This value is in agreement with the typical uncertainties reported in the literature.