2.5 Evaluation criteria
Here, the ET measured by the large-scale weighing lysimeters was the actual ET, and the performances of theET0 equations were compared to these lysimeter system estimates on a daily time step. The pair-wise comparisons were conducted using general linear regression. For further comparison, the root mean squared error (RMSE), percentage error of estimate (PE), mean absolute error (MBE) and coefficient of determination (R 2) were used for the evaluation of reference evapotranspiration models. The RMSE, PE, MBE andR 2 are defined as: