|LIN, LIAOMAO - Kansas State University|
|KUTIKOFF, SETH - Kansas State University|
|MAREK, THOMAS - Texas Agrilife Research|
|PORTER, DANA - Texas Agrilife Research|
Submitted to: ASABE Annual International Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 6/8/2016
Publication Date: 7/18/2016
Citation: Moorhead, J.E., Gowda, P., Marek, G.W., Lin, L., Kutikoff, S., Marek, T.H., Porter, D.O. 2016. Lysimetric evaluation of eddy covariance and scitillometer systems for the Texas High Plains. ASABE Annual International Meeting. ASABE 2016 international meeting, July 17-20, 2016, Orlando, FL.
Technical Abstract: Evapotranspiration (ET) is an important component in the water budget and used extensively in water planning and irrigation scheduling. Although lysimetry is considered the most accurate method for crop water use measurements, large precision weighing lysimeters are expensive to build and operate. Alternatively, other measurement systems such as eddy covariance (EC) and scintillometry are being used to estimate crop water use. However, issues have been widely acknowledged with both EC and scintillometry. Numerous studies have evaluated the measurement accuracy of scintillometers using eddy covariance systems; however, the energy balance closure problems with EC measurements may not allow for a thorough evaluation. In this study, an EC, infrared large aperture scintillometer (LAS), and visible surface layer scintillometer (SLS) were deployed in a lysimeter field at the USDA-ARS-Conservation and Production Research Laboratory in Bushland, TX for the 2015 growing season. Results indicated that the EC system produced the lowest error with an RMSE of 23%, when forcing energy balance closure by distributing the residual energy to latent heat flux. The SLS and LAS produced errors of 26% and 62%,respectively. All three instruments were found to have poor correlation for sensible heat flux, but good correlation with latent heat flux and ET. A combination approach of using the friction velocity and/or air density and specific heat of air from EC with the inputs from the scintillometers was employed in an attempt to increase the accuracy. However, the combinations for the EC-SLS did not increase the accuracy and the EC-LAS only obtained a minor reduction in RMSE. Further investigation involving an in-depth approach into the instrument theory and boundary layer physics may be necessary to explain if a combination of these instruments is potentially beneficial for measuring ET accurately.