Evaluating Surface Energy Balance System (SEBS) Using Aircraft Data Collected during BEAREX07

Abstract

Evapotranspiration (ET) is an essential component of the water balance and a major consumptive use of irrigation water and precipitation on cropland. Remote sensing based surface energy balance algorithms are now capable of providing accurate estimates of spatial-temporal ET. Uses of these spatial ET estimates are innumerable including hydrological modeling, irrigation scheduling, drought and flood monitoring and global climate change studies. The objective of this study was to evaluate the ability of the Surface Energy Balance System (SEBS) to estimate hourly ET fluxes using very high resolution (0.5-1.8 m) aircraft images acquired during the BEAREX07 (Bushland ET and Agricultural Remote Sensing Experiment 2007). Accuracy of the predicted ET fluxes were investigated using observed data from 4 large weighing lysimeters, each located at the center of 4.7 ha field in the USDA-ARS Conservation and Production Research Laboratory, Bushland, Texas. The uniqueness and the strength of this study come from the fact that it evaluates the SEBS for irrigated and dryland conditions simultaneously with each lysimeter field planted to irrigated forage sorghum, irrigated forage corn, dryland clumped-grain sorghum, and dryland row-grain sorghum. Eleven images acquired during early and mid cropping seasons (June 24 - July 27) were used in the study. SEBS algorithm performed equally well for both irrigated and dryland conditions in estimating the hourly ET with overall mean bias error and root mean square of -0.01 and 0.11 mm h 1 (-1.53% and 20.27%), respectively.