Estimating evapotranspiration using earth observation data: A comparison between hydrological and energy balance modelling approaches

Abstract

• Earth observation data is a useful alternate data source to hydrological models. • The spatial resolution of satellite data affects the accuracy of evapotranspiration. • The Surface Energy Balance System model outperformed the ACRU model. • Hydrological models should be developed to allow actual evapotranspiration input. Hydrological models are often applied to acquire estimates of evapotranspiration ( ET a ) using quality inputs of reference evapotranspiration ( ET 0 ). However, their application may be limited by the need for good quality long-term data inputs. In data scarce regions, the use of satellite-earth observation data as inputs to these models may provide a potential solution to overcome data acquisition challenges associated with conventional data collection approaches. In this study, the Agricultural Catchments Research Unit (ACRU) hydrological model was applied to estimate the ET a using both in-situ and satellite-derived estimates of ET 0 as inputs to the model. The simulated ET a estimates were then evaluated through comparisons against field-based measurements of ET a acquired from an Eddy Covariance system ( EC ET ), as well as from the application of the Surface Energy Balance System (SEBS) model. The results of these investigations demonstrated that the meteorologically-based ACRU ET a simulations marginally outperformed the satellite-based ACRU ET a simulations. While these results highlight the influence which the quality of ET 0 inputs may have on the accuracy of the ACRU derived ET a estimates, the concurrent application and evaluation of SEBS demonstrated that alternate approaches to hydrological modelling, may be better suited for ET a estimation in certain instances.