Diurnal Dynamics of Wheat Evapotranspiration Derived from Ground-Based Thermal Imagery

Abstract

Abstract:The latent heat flux, one of the key components of the surface energy balance, can be inferred from remotely sensed thermal infrared data. However, discrepancies between modeled and observed evapotranspiration are large. Thermal cameras might provide a suitable tool for model evaluation under variable atmospheric conditions. Here, we evaluate the results from the Penman-Monteith, surface energy balance and Bowen ratio approaches, which estimate the diurnal course of latent heat fluxes at a ripe winter wheat stand using measured and modeled temperatures. Under overcast conditions, the models perform similarly, and radiometric image temperatures are linearly correlated with the inverted aerodynamic temperature. During clear sky conditions, the temperature of the wheat ear layer could be used to predict daytime turbulent fluxes (root mean squared error and mean absolute error: 20-35 W·m 9776Errors are dependent on the models' ability to simulate diurnal hysteresis effects and are largest during intermittent clouds, due to the discrepancy between the timing of image capture and the time needed for the leaf-air-temperature gradient to adapt to changes in solar radiation. During such periods, we suggest using modeled surface temperatures for temporal upscaling and the validation of image data.

Evapotranspiration of the Brazilian Pampa Biome: Seasonality and Influential Factors

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Loops de histerese na evapotranspiração em área de pastagem no sul do Brasil

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Ground‐based infrared thermometry reveals seasonal evapotranspiration patterns in semiarid rangelands

“…The substantial overestimation of LE BR was observed even at MBS despite relatively sufficient moisture supply over the study period (Figure 7). Prior studies demonstrate good predictions of the Bowen Ratio-based method in LE over irrigated wheat (Ahrends et al, 2014) and herbaceous wetland plants (Hwang et al, 2020) in the temperate climate. These studies were conducted in well-watered conditions with little water stress.…”