Evaluating the Breathing Earth System Simulator's (BESS) Evaportranspiration Product over the Southern Great Plains of the United States

Scaling evapotranspiration (ET) from local measures to regional and global values is a critical task as improved understanding of ET processes can benefit weather and climate analysis and prediction, water management, and agriculture. This study examined the ET values produced by the Breathing Earth System Simulator (BESS) over the Southern Great Plains (SGP) of the United States. BESS is a global land surface model that estimates ET from 2000-2015 with a horizontal resolution of 1 km using instantaneous snapshots of satellite data upscaled to daily and 8-day products. The BESS values were compared with 15 eddy covariance flux towers with 59 site-years of observations over the SGP domain. The results show that the 8-day BESS ET values (R² = .76) represent ET better than the MODIS (R² = .62) 8-day ET products within the study area, and the interannual variability of estimated ET versus observed ET were very similar at a site-by-site scale. Further, spatiotemporal patterns during 2000-2015 were distinguishable over the SGP and captured anomalous events produced by varying meteorological conditions. Finally, the BESS-derived drought index (ratio of ET to potential ET) captured the evolution and magnitude of the 2011 drought event.