Evaluation of Satellite Images and Products for the Estimation of Regional Reference Crop Evapotranspiration in a Valley of the Ecuadorian Andes

Abstract

The capabilities of images and products obtained by four satellite sensors with different spatial and temporal resolutions (LANDSAT 8, ASTER, MODIS and SENTINEL 3) were analyzed as inputs for the calculation of the reference crop evapotranspiration (ETo). The FAO Penman-Monteith equation was: (a) used in a traditional way, to calculate local values of ETo using data recorded in the existing meteorological stations in the study area; and (b) applied to estimate the regional ETo using the images and products obtained through remote sensing. The capabilities of the satellite products selected were evaluated by means of cross-validation, comparing the values obtained by the meteorological stations to the corresponding values extracted from the regional evapotranspiration maps. The coefficient of determination (R2), the Nash–Sutcliffe efficiency (NSE) and the root mean square error (RMSE) were calculated. The results of the study show that there is a direct correlation between the spatial resolution and the accuracy of the ETo estimates, the products of LANDSAT 8 being those that reached the greatest accuracy. Nevertheless, for continuous ETo monitoring, SENTINEL 3 is preferred.