Abstract

This study aimed to apply the Mapping Evapotranspiration at high Resolution with Internalized Calibration (METRIC) model to estimate surface energy balance and daily actual evapotranspiration (ETa) for sugarcane crop in the administrative region of Ribeirão Preto, São Paulo State, using Landsat images from 2005 and 2007. Estimates generated were compared to observed data from a flux tower site, and the performance of the equations based on physical principles and empirical equations was evaluated. The net radiation (Rn) was equal to the observed values, considering a confidence level of 95%, with R²=0.87, MAE=54.79 W.m-2 and RMSE= 64.47, showing a good performance of METRIC when modeling this variable based on physical laws. Soil heat flux (G) was estimated from an empirical equation and presented no satisfactory performance, underestimating the values by 34%. The internal calibration of sensible heat flux (H) allowed this term to absorb errors of Rn and G, leading to satisfactory values of latent heat flux (LE) and ETa. Results of t-test indicated that the estimated values of latent heat flux were equal to the observed data with a confidence level of 95%, showing R²=0.86, MAE=13.93 W.m-2 and RMSE= 25.36. The estimated ETa was also equal to the values observed, according to the t-test with a confidence level of 95%, presenting R²=0.85, MAE=0.37 mm.day-1 and RMSE= 0.49