# Estimating ET Using Turbulent Coherent Structures

*by*R. L. Snyder, Univ of California, Davis, United States,

K. T. Paw U, Univ of California, Davis, United States,

**Abstract:**Two methods for estimating sensible heat flux to use in energy balance equations for computing crop evapotranspiration are discussed. The methods use high frequency temperature measurements at canopy height and turbulent coherent structure theory to analyze temperature trace ramp patterns. In both methods, the temperature change with time is used to estimate the sensible heat flux density. In the first method, calibration is accomplished by regressing a predicted sensible heat flux against eddy-correlation sensible heat flux. In the second method, temperature data that are influenced by advection are filtered and the sensible heat flux is estimated using a partial derivative of temperature change with time. Crop evapotranspiration is then estimated from a basic energy balance using measured net radiation and soil heat flux and the sensible heat flux estimated from high frequency temperature data.

**Subject Headings:**Evapotranspiration | Crops | Thermal analysis | Temperature effects | Regression analysis | Structural analysis | Energy measurement

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