a Department of Plant and Environmental Sciences, Box 30003, MSC3Q, New Mexico State University, Las Cruces, NM 88003, USA b Department of Natural Resources Management and Engineering, University of Connecticut, Storrs, CT 06269-4087, USA
Eddy covariance technology has been used for crop water use measurements (evapotranspiration, ET) widely because its operation is relatively simple and the equipment is less expensive than constructing a lysimeter. However, this technology has energy closure problems. These problems can be caused by low wind speed, stable conditions, horizontal flux or/and canopy roughness. In addition, wind sensor leveling, air humidity, and footprint can affect the ET measurement accuracy. This commentary discusses how to check ET measurement accuracy and how to measure accurate ET using eddy covariance technology.
Current measurement methods for crop water use (evapotranspiration, ET) mainly include lysimeter, eddy covariance, energy balance, surface renewal, Bowen ratio, and remote sensing technologies. Lysimeter measurement of ET is the standard, Eddy covariance represents the next level of accuracy, and the other methods follow.
Eddy covariance technology has been used widely because of its relatively simple operation and lower expense for equipment compared to constructing a lysimeter. An eddy covariance system consists of a vapor concentration sensor (e.g., infrared open-path Licor-7500, Campbell Sci., Inc., Logan, Utah) and a high-frequency sonic wind velocity sensor
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