Provides functions to estimate daily reference evapotranspiration
(ET0) using 10 radiation-based empirical models, with the Food and
Agriculture Organization (FAO) Penman-Monteith method included as the
standard reference for model comparison. Includes statistical evaluation
metrics, such as Nash-Sutcliffe efficiency (NSE), root mean square error
(RMSE), mean absolute error (MAE), and mean bias error (MBE), and
visualization tools (scatter plots and Taylor diagrams). Based on
Singh et al. (2026)