Comparison of Four Different Energy Balance Models for Estimating Evapotranspiration in the Midwestern United States

The development of different energy balance models has allowed users to choose a model based on its suitability in a region. We compared four commonly used models- Mapping EvapoTranspiration at high Resolution with Internalized Calibration ( METRIC) model, Surface Energy Balance Algorithm for Land ( SEBAL) model, Surface Energy Balance System ( SEBS) model, and the Operational Simplified Surface Energy Balance ( SSEBop) model- using Landsat images to estimate evapotranspiration ( ET) in the Midwestern United States. Our models validation using three AmeriFlux cropland sites at Mead, Nebraska, showed that all four models captured the spatial and temporal variation of ET reasonably well with an R2 of more than 0.81. Both the METRIC and SSEBop models showed a low root mean square error (< 0.93 mm center dot day -1) and a high Nash- Sutcliffe coefficient of efficiency (> 0.80), whereas the SEBAL and SEBS models resulted in relatively higher bias for estimating daily ET. The empirical equation of daily average net radiation used in the SEBAL and SEBS models for upscaling instantaneous ET to daily ET resulted in underestimation of daily ET, particularly when the daily average net radiation was more than 100 W center dot m - 2. Estimated daily ET for both cropland and grassland had some degree of linearity with METRIC, SEBAL, and SEBS, but linearity was stronger for evaporative fraction. Thus, these ET models have strengths and limitations for applications in water resource management.