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Sensors 2017, 17(10), 2350; https://doi.org/10.3390/s17102350

Evaluation of Sensible Heat Flux and Evapotranspiration Estimates Using a Surface Layer Scintillometer and a Large Weighing Lysimeter

1
USDA-ARS Conservation and Production Research Laboratory, PO Drawer 10, Bushland, TX 79012, USA
2
USDA-ARS Grazinglands Research Laboratory, 7207 West Cheyenne St., El Reno, OK 73036, USA
3
Texas A&M AgriLife Research, 6500 Amarillo Blvd W, Amarillo, TX 79106, USA
4
Texas A&M AgriLife Extension Service, 1102 E FM 1294, Lubbock, TX 79403, USA
*
Author to whom correspondence should be addressed.
Received: 8 September 2017 / Revised: 10 October 2017 / Accepted: 12 October 2017 / Published: 14 October 2017
(This article belongs to the Special Issue Sensors in Agriculture)
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Abstract

Accurate estimates of actual crop evapotranspiration (ET) are important for optimal irrigation water management, especially in arid and semi-arid regions. Common ET sensing methods include Bowen Ratio, Eddy Covariance (EC), and scintillometers. Large weighing lysimeters are considered the ultimate standard for measurement of ET, however, they are expensive to install and maintain. Although EC and scintillometers are less costly and relatively portable, EC has known energy balance closure discrepancies. Previous scintillometer studies used EC for ground-truthing, but no studies considered weighing lysimeters. In this study, a Surface Layer Scintillometer (SLS) was evaluated for accuracy in determining ET as well as sensible and latent heat fluxes, as compared to a large weighing lysimeter in Bushland, TX. The SLS was installed over irrigated grain sorghum (Sorghum bicolor (L.) Moench) for the period 29 July–17 August 2015 and over grain corn (Zea mays L.) for the period 23 June–2 October 2016. Results showed poor correlation for sensible heat flux, but much better correlation with ET, with r2 values of 0.83 and 0.87 for hourly and daily ET, respectively. The accuracy of the SLS was comparable to other ET sensing instruments with an RMSE of 0.13 mm·h−1 (31%) for hourly ET; however, summing hourly values to a daily time step reduced the ET error to 14% (0.75 mm·d−1). This level of accuracy indicates that potential exists for the SLS to be used in some water management applications. As few studies have been conducted to evaluate the SLS for ET estimation, or in combination with lysimetric data, further evaluations would be beneficial to investigate the applicability of the SLS in water resources management. View Full-Text
Keywords: irrigation; energy balance; water management; semi-arid regions irrigation; energy balance; water management; semi-arid regions
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Moorhead, J.E.; Marek, G.W.; Colaizzi, P.D.; Gowda, P.H.; Evett, S.R.; Brauer, D.K.; Marek, T.H.; Porter, D.O. Evaluation of Sensible Heat Flux and Evapotranspiration Estimates Using a Surface Layer Scintillometer and a Large Weighing Lysimeter. Sensors 2017, 17, 2350.

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