ESTIMATION OF THE ACCURACY OF THE CALCULATION OF REFERENCE AND ACTUAL EVAPOTRANSPIRATION BASED ON VIRTUAL WEATHER STATION DATA FOR POLISSYA REGION OF UKRAINE
Abstract
This article evaluates the accuracy of calculating reference and actual evapotranspiration using Virtual Visual Crossing Weather Data (VCWD) and automatic iMetos Base meteorological station data in Polissya, Ukraine. The study confirmed the feasibility of calculating ETo and ETc using VCWD meteorological data. The ETo calculation is 86,1% accurate, with an RMSE and SEE error of 0,76 and 0,49 mm, respectively. The ETo calculation with correction factors for meteorological data increases its accuracy by 1,4%, and the RMSE error decreases by 0,08 mm. The most accurate calculations were obtained using a correction factor of 1,1 to the calculated ETo. With the correction factor applied, the ETo determination accuracy is 88,9%, with RMSE and SEE errors of 0,58 and 0,54 mm, respectively. The ETo data from VCWD were obtained with satisfactory accuracy; the largest errors in the MAPE, RMSE, and SEE were 20,4%, 1.09 mm, and 1,02 mm, respectively. For 2023–2024, the FEA, RMSE, and SEE errors for ETo calculated from VCWD meteorological data, accounting for the 1,1 correction factor, were 10,0–12,2%, 0,55–0,60, and 0,51–0,55 mm, respectively. During the research period, the MAPE, RMSE, and SEE errors for this variant were 9,0%-14,0%, 0,52-0,63 mm, and 0,34-0,56 mm, respectively. The calculation of absolute errors in determining ETo confirms that the most reliable data of reference evapotranspiration are obtained using the correction factor. This option resulted in the smallest average absolute error by years of research, which is 5 mm, and in 2024 this error was 0. In terms of months, the smallest absolute error of 2 mm was observed in May and August, and the largest -13 mm in September.
The results of the calculations of actual evapotranspiration (ETc) of crops showed that using a correction factor of 1,1 to ETo increases the accuracy of ETc calculations. The mean absolute relative error (MAPE) decreased by 2,1% for all crops, and the root mean square error (RMSE) decreased by 0,16, 0,15, and 0,09 mm for corn, potatoes, and blueberries, respectively. The average absolute ETc errors by year of research using a correction factor of 1,1 for ETo were 15,7, and 11 mm for corn, potatoes, and blueberries, respectively. In May, June, and July, the calculated ETc for corn seed was 11,6, and 8 mm lower than the actual values. In August and September, it was 1 and 9 mm higher, respectively. This trend in the errors distribution is also observed for potatoes and blueberries.
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