Modification of the radiation-based Abtew reference evapotranspiration model under humid climate, Northeast India

Abstract

In this work, seven models of temperature-based solar radiation were used to enhance the Abtew model for ET0 calculation in Northeast India. The only input data needed for the temperature-based models are air temperature, which can be easily measured in most locations worldwide. Under the climatic conditions of Dibrugarh, Northeast India, the applicability of the improved Abtew models (A1–A7), the Stephen-Stewart model (SS), the Irmak model (Ir), and the Modified Turc model (MT) was assessed. Utilizing statistical indices such as mean absolute error (MAE), root-mean-square error (RMSE), standard error (SE), coefficient of correlation (r), coefficient of determination (R2), and index of agreement (D), the performances of all the modified equations (A1–A7) and other chosen ET0 models have been compared. The findings demonstrated that for ET0 estimate at Dibrugarh, the seven upgraded Abtew models (RMSE = 0.44–0.50 mm/day; D = 0.81–0.88) outperformed the four physical models (RMSE = 0.50–2.77 mm/day; D = 0.49–0.82). In the end, the A6 model won the top spot based on many statistical factors. Utilizing the temperature-based solar radiation model significantly increased the Abtew model estimation accuracy. It is strongly advised to estimate ET0 using the A6 model, which needs temperature as input data.