Abstract
Accurate estimation of reference evapotranspiration is a key step in irrigation and water resources planning. The Penman Monteith (FAO56-PM) formula recommended by FAO56-PM is the standard for calculating the reference evapotranspiration. However, the FAO56-PM model is limited in the observation of meteorological variables, so it is necessary to choose an alternative ET0 model which requires less meteorological data. Based on the daily climate data of eight meteorological stations in northern Xinjiang from 2000 to 2020, seven empirical models (Hargreaves, Berti, Dorji, Dalton, Meyer, WMO, Albrecht) and four optimization algorithms (RF model, LS-SVR model, Bi-LSTM model and GA-BP model) combined with seven different parameters were evaluated comprehensively. The results show that the accurate of the empirical model based on temperature is obviously better than the empirical model based on air mass transport. The annual and multi-year alternative ET0 models of different input parameter combinations are: LS-SVR1, RF2, LS-SVR3, LS-SVR4, GA-BP5, LS-SVR6, GA-BP7. It can be used as a substitute for the reference evapotranspiration model without relevant meteorological data. Only the LS-SVR6 model and GA-BP7 model are recommended as the best alternative models for northern Xinjiang reference evapotranspiration at daily, monthly and seasonal scales.
Highlights
The quantification and accurate estimation of evapotranspiration are of great significance to the formulation of farmland irrigation systems, the study of hydrology and water balance, and the planning of water resources
Xinjiang; (2) to use the global performance index global performance indicator (GPI) to rank the 28 models based on the optimization algorithm and to determine the best algorithm model under seven different parameter input combinations; and (3) to discuss the influence of time scale on the model and to recommend the most appropriate reference evapotranspiration estimation model for northern Xinjiang at different time scales
The WMO model and Meyer model have poor simulation effects. This finding indicates that the model based on air mass transport has poor applicability in northern Xinjiang, which further proves that temperature is the decisive factor affecting ET0 in northern Xinjiang
Summary
The quantification and accurate estimation of evapotranspiration are of great significance to the formulation of farmland irrigation systems, the study of hydrology and water balance, and the planning of water resources. This method does not need to be initially calibrated locally and has global applicability [4,5,6] This method has many input parameters (air temperature, humidity, solar radiation and wind speed), so the acquisition of many meteorological parameters becomes the only limitation of its application [7]. In this case, relatively simple empirical models are usually used to estimate ET0 , and the selection of the optimal empirical model is of great significance to water resource planning and management [8,9]. The ET0 model based on temperature and air mass transport was selected in this study to verify its applicability in northern Xinjiang
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