Surface energy balance model of transpiration from variable canopy cover and evaporation from residue-covered or bare soil systems: model evaluation

Abstract

A surface energy balance model (SEB) was extended by Lagos et al. Irrig Sci 28:51-64 (2009 )t o estimate evapotranspiration (ET) from variable canopy cover and evaporation from residue-covered or bare soil systems. The model estimates latent, sensible, and soil heat fluxes and provides a method to partition evapotranspira- tion into soil/residue evaporation and plant transpiration. The objective of this work was to perform a sensitivity analysis of model parameters and evaluate the performance of the proposed model to estimate ET during the growing and non-growing season of maize (Zea Mays L.) and soy- beans (Glycine max) in eastern Nebraska. Results were compared with measured data from three eddy covariance systems under irrigated and rain-fed conditions. Sensitivity analysis of model parameters showed that simulated ET was most sensitive to changes in surface canopy resistance, soil surface resistance, and residue surface resistance. Comparison between hourly estimated ET and measure- ments made in soybean and maize fields provided support for the validity of the surface energy balance model. For growing season's estimates, Nash-Sutcliffe coefficients ranged from 0.81 to 0.92 and the root mean square error (RMSE) varied from 33.0 to 48.3 W m -2 . After canopy closure (i.e., after leaf area index (LAI = 4) until harvest), Nash-Sutcliffe coefficients ranged from 0.86 to 0.95 and RMSE varied from 22.6 to 40.5 W m -2 . Performance prior to canopy closure was less accurate. Overall, the evaluation of the SEB model during this study was satisfactory.