Evaluation of applicability of three evapotranspiration models using meteorological data

The applicability of three models used to estimate the evapotranspiration based on general meteorological data is analyzed. The models include the advection-aridity (AA) model, Granger model and the improved Penman-Monteith model proposed by Katerji and Perrier, namely P-M-Katerji model. The dimensionless analysis method is applied, by which the ratio of actual evapotranspiration to Penman potential evapotranspiration is expressed as a function of the proportion of the radiation term in Penman potential evapotranspiration. The three models use different functions, and the applicability of each model is analyzed according to the characteristics of the functions respectively. It is found that the AA model is applicable to the environment which is neither extreme dry nor extreme wet, it underestimates the actual evapotranspiration under dry conditions but overestimates under wet conditions. The Granger model is applicable to the conditions with a wide range of evapotranspiration ratio, and it is approximately equivalent to the AA model under ordinary wet condition. The simulation result of the P-M-Katerji model is not very good if the variation range of evapotrnaspiration is wide. The validity of the analysis result is verified by a case study.