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

Hydrological models are often applied to acquire estimates of evapotranspiration (ETa) using quality inputs of reference evapotranspiration (ET0). 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 ETa using both in-situ and satellite-derived estimates of ET0 as inputs to the model. The simulated ETa estimates were then evaluated through comparisons against field-based measurements of ETa acquired from an Eddy Covariance system (ECET), 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 ETa simulations marginally outperformed the satellite-based ACRU ETa simulations. While these results highlight the influence which the quality of ET0 inputs may have on the accuracy of the ACRU derived ETa estimates, the concurrent application and evaluation of SEBS demonstrated that alternate approaches to hydrological modelling, may be better suited for ETa estimation in certain instances. © 2022 Elsevier B.V.