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: