EVAPOTRANSPIRATION ASSESSMENT USING THE PT-JPL MODEL WITH ERA5-LAND REANALYSIS DATA

Authors:Dobrokhotov Aleksei V., Kozyreva Ludmila V., Mukhina Daria P.

536.423.1:528.8
Theme: Land reclamation, water manadgement and agrophysics
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Purpose: to assess the feasibility of integrating radiation flow data from the ERA5-Land climate reanalysis into an energy balance model that determines the spatial distribution of evapotranspiration in the absence of satellite thermal imaging data and to validate the modified model using an irrigated soybean field in the Saratov region as an example.

Materials and methods. PT-JPL was used as an energy balance model. A scheme for replacing the radiation balance calculation block with ERA5-Land reanalysis data with a preliminary correction for systematic bias based on in-situ measurements is proposed. The method was validated by comparing it with in-situ evapotranspiration measurements at pulse stations.

Results. A comparative analysis showed that the initial ERA5-Land reanalysis data systematically underestimated the radiation balance values compared to the PT-JPL calculation method (determination coefficient R² = 0.59, percentage bias PBias = 11.3 % versus R² = 0.73 and PBias = 2.5 %). The introduction of a correction coefficient (~1.11) improved the quality of the input reanalysis data: R² increased to 0.69, and PBias decreased to 1.3 %. Subsequent evapotranspiration modeling using the updated radiation balance from ERA5-Land demonstrated almost complete identity with the original PT-JPL method (R² = 0.47, RMSE = 0.12 mm/h, PBias = −0.4 %). Testing on an irrigated soybean field in the Saratov region showed that the absolute differences between the methods in estimating evapotranspiration do not exceed 0.03 mm/h.

Conclusions. The proposed modification of the PT-JPL model allows for obtaining adequate estimates of the spatial distribution of evapotranspiration components using ERA5-Land reanalysis data instead of the calculation block requiring a thermal channel. This expands the applicability of the model in combination with data from satellites or UAVs not equipped with thermal sensors.

doi: 10.31774/2712-9357-2026-16-2-106-126

Keywords

radiation balance, transpiration, evaporation from the soil surface, turbulent pulsation method, Earth remote sensing, Landsat, bias correction

For quoting

Dobrokhotov A. V., Kozyreva L. V., Mukhina D. P. Evapotranspiration assessment using the PT-JPL model with ERA5-Land reanalysis data. Land Reclamation and Hydraulic Engineering. 2026;16(2):106–126. (In Russ.). https://doi.org/10.31774/2712-9357-2026-16-2-106-126.

Authors

A. V. Dobrokhotov – Senior Researcher of the Department of Soil Physics, Physical Chemistry and Biophysics, Candidate of Biological Sciences, Agrophysical Research Institute (195220, Saint-Petersburg, Grazhdanskiy ave., 14), adobrokhotov@agrophys.ru, ORCID: 0000-0002-9368-6229;

L. V. Kozyreva – Researcher of the Department of Soil Physics, Physical Chemistry and Biophysics, Candidate of Technical Sciences, Agrophysical Research Institute (195220, Saint-Petersburg, Grazhdanskiy ave., 14), 4ludak@gmail.com, ORCID: 0000-0001-7990-8211;

D. P. Mukhina – Postgraduate Student of the Department of Soil Physics, Physical Chemistry and Biophysics, Agrophysical Research Institute (195220, Saint-Petersburg, Grazhdanskiy ave., 14), darin.m.19.13.21@gmail.com, ORCID: 0009-0003-1654-7000.

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