Estimating Evapotranspiration From Satellite Using Easily Obtainable Variables: A Case Study Over the Southern Great Plains, USA

English (OpenAlex)

Evapotranspiration (ET) is a critical component of the earth's water budget, a critical modulator of land-atmosphere interactions, and also plays a crucial role in managing the earth's energy balance. In this study, the feasibility of generating spatially continuous daily evaporative fraction (EF) and ET from minimal remotely sensed and meteorological inputs in a trapezoidal framework is demonstrated. A total of four variables, normalized difference vegetation index, land surface temperature (Ts), gridded daily average temperature (Ta), and elevation (z) are required to estimate EF. Then, ET can be estimated with the available soil heat flux (G) and net radiation (Rn) data. First, the crucial model variable Ts- Tais examined how well it characterizes the variation in EF using in-situ data recorded at two eddy correlation flux towers in Southern Great Plains, USA in 2011. Next, the accuracy of satellite-based Tsis compared to ground-based Ts. Finally, EF and ET estimates are validated. The results reveal that the model performed satisfactorily in modeling EF and ET variation at winter wheat and deciduous forest during the high evaporative months. Even though the model works best with the observed Moderate Resolution Imaging Spectroradiometer-Tsas opposed to temporally interpolated Ts, results obtained from interpolated Tsare able to close the gaps with reasonable accuracy. Due to the fact that Ts- Tais not a good indicator of EF outside the growing season when deciduous forest is dormant, potential improvements to the model are proposed to improve accuracy in EF and ET estimates at the expense of adding more variables.