Modeling evapotranspiration and energy balance in a wheat-maize cropping system using the revised RZ-SHAW model

Correctly simulating evapotranspiration (ET) and surface energy balance is essential to simulating crop growth under water and heat stress conditions in agricultural systems. The revised hybrid model (RZ-SHAW), combining the Root Zone Water Quality Model (RZWQM) and Simultaneous Heat and Water (SHAW) model, was evaluated for simulating ET and surface energy balance components against observed data from an eddy covariance system in a wheat-maize double cropping system in the North China Plain (NCP), after it was calibrated for soil water content and crop growth. The average daily ET was slightly under-simulated by 0.05 mm in the wheat seasons and over-simulated by 0.23 mm in the maize seasons, compared with the observed latent heat flux (LE) from 2003 to 2005. The root mean squared error (RMSE) and model efficiency (ME) of simulated daily ET were 0.59 mm and 0.86 for the three years. The goodness of simulation for Rn (net radiation), LE, H (sensible heat flux) and canopy temperature was better in the middle crop seasons than in the early crop seasons. The RMSE values for simulated Rn, H, LE, G (ground heat flux), and canopy temperature were 31.9, 37.2, 37.9, 21.8 W m−2, and 1.37 °C, respectively, for middle wheat seasons and were 29.2, 27.1, 29.7, 19.7 W m−2, and 1.22 °C, respectively, for middle maize seasons. These simulation results were comparable with previous modeling studies, indicating that the revised hybrid model is reasonable for simulating ET, surface energy balance as well as crop growth in the double cropping system.