Performance of different methods to estimate reference evapotranspiration in Cruz Alta - RS
The objective of this work was to evaluate the performance of different methods to estimate reference evapotranspiration (ETo) in the municipality of Cruz Alta - RS, using the Penman-Monteith method as standard. Daily meteorological data were collected from the Automatic Meteorological Station of the National Meteorological Institute (INMET), located in the municipality of Cruz Alta - RS, for a 10-year period. ETo was determined using the methods of Penman-Monteith, Priestley-Taylor, Hargreaves-Samani, Benevides-Lopes and Jensen-Haise, comparing the standard method with the other methods used for three subgroups of data: analysis of the average of 10 years of observations and periods of high and low solar radiation. In order to establish the best methods for estimating ETo, we used: linear regression analysis, root mean square error (RMSE), mean absolute error (MAE), agreement index (d), and performance index (c), with classes established by Camargo and Sentelhas. Among the methods evaluated for the climatic conditions of Cruz Alta - RS, the Priestley-Taylor method is the one that presents the best performance in ETo estimation, followed by the Hargreaves-Samani method, which can be used in daily and annual determinations, and in periods of high solar radiation. Due to the poor performance presented by the Jensen-Haise method, its use is not recommended.