Evapotranspiration (ET) is an important variable in the hydrologic cycle. As such, improved understanding of the spatial and temporal variability of ET is critical to weather and climate analysis and prediction, water management resources, agriculture, land-use and land-change projects, and ecological research. Eddy covariance flux towers were deployed over grasslands and winter wheat at the United States Department of Agriculture site near El Reno, Oklahoma and at the Marena Oklahoma In-Situ Sensor Testbed (MOISST). Ten total years of surface energy, water, and carbon fluxes were paired with fifty total years of data from twelve additional flux towers across the Southern Great Plains (SGP) for a regional land-surface analysis using the Breathing Earth System Simulator (BESS). BESS is a land-surface model that couples land-atmosphere processes to estimate ET and gross primary production (GPP). The study results verify that BESS produces better ET values for the SGP than several other ET models.
An overview of the data that were collected at in-situ eddy covariance flux towers and comparison with BESS will be presented. Additionally, BESS ET was computed across the SGP from 2000-2015 and spatial and temporal analyses were used to quantify the variability of ET across the SGP. Further, precipitation data was compared with ET values to determine the magnitude of precipitation partitioned to ET in the regional water budget. Finally, a sensitivity analysis of BESS was performed to illuminate which variables influence the BESS ET estimates across varying climatological conditions.