Thermal scanner measurement of canopy temperatures to estimate evapotranspiration

Temperatures of soybean (Glycine max L.), sorghum (Sorghum bicolor L.), and millet (Panicum miliaceum L.), measured with a thermal scanner flown at altitudes of 610 and 1220 m, were used in a resistance form of the energy-balance equation to estimate evapotranspiration (ET). Atmospheric attenuation produced errors of 1 to 6 °C in the scanner measurements. Errors from neglecting emissivity corrections were less than 1.0 °C. A correction procedure relating temperature error to atmospheric precipitable water was applied to the scanner measurements. Estimates of ET using the corrected temperatures differed from lysimetric measurements by -0.40 to 0.1 7 ly/min. It was found that accurately extrapolating scanner measurements to ground level was essential for estimating ET. © 1976.

Thermal scanner measurement of canopy temperatures to estimate evapotranspiration Academic Article