Comparison of remote sensing-based energy balance methods for estimating crop evapotranspiration

Remote sensing of evapotranspiration has become more common during the last decade. Two of the approaches being used are the reflectance-based crop coefficient method and the energy balance method. In the energy balance approach, surface temperature is used to calculate sensible heat flux and long wave radiation and depending on the complexity of the model, different methods are used to handle the aerodynamic temperature term. This paper compares two energy balance approaches with different methodology for estimating sensible heat flux (H): (i) one layer energy balance model and (ii) two-layer energy balance model called the Two Source Model. The results from the two approaches are compared using a set of comprehensive field and remote sensing measurements of model input data and actual evapotranspiration measured with a dense network of eddy covariance stations during the SMACEX campaign in central Iowa during the 2002 growing season. Results show that both methods of estimating H perform well using calibrated Landsat Thematic Mapper imagery as remotely sensed inputs.