Evapotranspiration estimation using high-resolution aerial imagery and pySEBAL for processing tomatoes

The use of high-resolution aerial imagery for assessing actual crop evapotranspiration (ETₐ) holds the potential to optimize the use of limited water resources in agriculture. Despite this potential, there is a shortage of information regarding the effectiveness of energy balance algorithms, initially designed for satellite remote sensing in estimating ETₐ using aerial imagery. This study addresses this gap by employing the remote sensing model pySEBAL (Surface Energy Balance Algorithm for Land) in conjunction with high-resolution aerial imagery to estimate ETₐ for processing tomatoes. Throughout the 2021 growing season, an aircraft captured multispectral and thermal imagery over a processing tomato field near Esparto, California, USA. Simultaneously, an eddy covariance flux tower within the field measured high-frequency turbulent fluxes and low-frequency biometeorology variables essential for evaluating the energy balance. The comprehensive assessment of energy balance components, including ETₐ , yielded compelling evidence that pySEBAL accurately estimated ETₐ at high spatial resolution. The root mean square error (RMSE) and normalized RMSE for various energy balance components were as follows: 33 W m − 2 (12%) for latent heat flux, 29 W m − 2 (35%) for sensible heat flux, 24 W m − 2 (4%) for net radiation, and 10 W m − 2 (15%) for soil heat flux. Additionally, ETₐ exhibited an RMSE and NRMSE of 0.26 mm d − 1 (6%). Moreover, the spatial mapping of ETₐ across the processing tomato field visually depicted the spatial variability associated with irrigation scheduling, crop development, areas affected by disease, and soil heterogeneity. This research underscores the value of high resolution spatial aerial imagery and pySEBAL algorithm for estimating ETₐ variability in the field, a crucial aspect for guiding precision irrigation management and ensuring the optimal use of limited water resources in agriculture.