Location: Soil and Water Management Research
Title: An Evaluation of SEBAL Algorithm Using High Resolution Aircraft Data Acquired During BEAREX07 Authors
Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: December 15, 2010
Publication Date: December 16, 2010
Citation: Paul, G., Gowda, P., Vara Prasad, P., Howell, T.A., Staggenborg, S. 2010. An Evaluation of SEBAL Algorithm Using High Resolution Aircraft Data Acquired During BEAREX07 [abstract]. American Geophysical Union Meeting, December 13-17, 2010, San Francisco, California. Paper No. H23J-05. Technical Abstract: Surface Energy Balance Algorithm for Land (SEBAL) computes spatially distributed surface energy fluxes and evapotranspiration (ET) rates using a combination of empirical and deterministic equations executed in a strictly hierarchical sequence. Over the past decade, SEBAL has been tested over various regions and has found its application in solving water resources and irrigation problems. This research combines high resolution remote sensing data and field measurements of surface radiation and agro-meteorological variables to review various SEBAL steps for mapping ET in the Texas High Plains (THP). High resolution aircraft images (0.5-1.8 m) acquired during the Bushland Evapotranspiration and Agricultural Remote Sensing Experiment 2007 (BEAREX07) conducted at the USDA-ARS Conservation and Production Research Laboratory in Bushland, Texas, were utilized to evaluate the SEBAL. Accuracy of individual relationships and predicted ET values were investigated using observed hourly ET rates from four large weighing lysimeters, each located at the center of a 4.7 ha field. The uniqueness and the strength of this study come from the fact that it evaluates the SEBAL 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 sorghum. Improved coefficients for the local conditions were developed for the computation of roughness length for momentum transport. The decision involved in selection of dry and wet pixels, which essentially determines the partitioning of the available energy between sensible (H) and latent (LE) heat fluxes, is discussed. The difference in roughness length referred to as the kB**-1 parameter was modified in the current study. Performance of the SEBAL was evaluated using mean bias error (MBE) and root mean square error (RMSE). A RMSE of +/- 37.68 W m**-2 and +/- 0.11 mm h**-1 were observed for the net radiation and hourly actual ET, respectively. Application of SEBAL over THP shows promising prospects for water management, however, locally devolved relations, careful selection of dry and wet pixel, and calibration are required for good performance.