EVALUATION OF THE ACCURACY OF EVPOTRANSPIRATION IN THE EVAPO MOBILE APPLICATION

Abstract The article presents the results of the study on the accuracy of evapotranspiration in the EVAPO mobile application. The aim of the work is to provide recommendations on the effective use of the mobile application for the prompt, low-cost and convenient determination of evapotranspiration and planning the irrigation regime. Materials and methods. The study was conducted in the autumn of 2020 and in the summer of 2021 using meteorological data from Kherson Regional Hydrometeorological Station, which were used for reference calculations of evapotranspiration according to the method recommended by FAO (Penman-Monteith equation) in the ETo Calculator software. The calculated values of the reference evapotranspiration and those obtained in the EVAPO mobile application were compared with each other through the computation of the correlation coefficients, determination coefficients and mean absolute percentage errors to assess the accuracy of the data on the studied agrometeorological index in the mobile application. Statistical calculations and graphical models were performed using Microsoft Excel 365 spreadsheet processor. Polynomial regression was applied to calibrate and enhance the performance of original EVAPO application. Results. It was found that the EVAPO mobile application without additional calibration cannot provide the proper accuracy of the evapotranspiration calculation. During the cold period of the year (October-November) the mean absolute percentage error was 137.02 %, and during the warm period (May-August) it was 41.43 %. The general error of the calculation in the mobile application compared to the ETo Calculator reference values was 88.75 %. At the same time, EVAPO makes it possible to accurately track the trend of evapotranspiration dynamics, the coefficient of determination of the model is 0.86. In the warm period of the year, there is a tendency to overestimate the value of evapotranspiration, and in the cold period of the year, no clear pattern was found. The evapotranspiration values adjusted by the polynomial regression model obtained in the EVAPO mobile application allow their use in operational irrigation planning. Conclusions. The EVAPO mobile application is a convenient, accessible tool for the rapid assessment of evapotranspiration. However, its implementation on the territory of Ukraine cannot be recommended without preliminary calibration for each specific agroclimatic zone due to enormous errors in the estimation of evapotranspiration value.