ET Mapping with METRIC Algorithm Using Airborne High Resolution Multispectral Remote Sensing Imagery

Routine and accurate estimates of spatially distributed evapotranspiration (ET) are essential for managing water resources particularly in irrigated regions such as the U.S. Southern High Plains. For instance, ET maps would assist in the improvement of the Ogallala aquifer ground water management. METRIC (Mapping ET at high Resolutions with Internal Calibration) is an energy balance algorithm, which was developed for application with Landsat imagery, for monitoring distributed actual ET at a regional scale. METRIC has not been evaluated in a highly advective environment like the Texas High Plains using high resolution airborne visible and thermal remote sensing imagery. METRIC was evaluated using data from the Bushland Evapotranspiration and Agricultural Remote Sensing Experiment (BEAREX07) that was conducted during the 2007 cropping season in and around the USDA-ARS, Conservation and Production Research Laboratory (CPRL) in Bushland, Texas. As part of this experiment, high resolution aircraft imagery (0.5 m pixel size in the visible and near infrared bands and 1.8 m in the thermal band) were acquired using the Utah State University airborne multispectral digital system. During the overpasses, ground truth data were collected for surface short-wave reflectance and long-wave thermal emittance, soil water content, crop parameters, and net radiation measurements. Data from four large precision weighing lysimeters, in sorghum and corn fields, at the CPRL were used for evaluating METRIC daily ET predictions.