Infrared surface temperature (T{sub}s) has been considered a practical approximation of the true aerodynamic temperature (T{sub}o). Once shown that the two temperatures are basically not the same, a new interpretation of T{sub}s became a necessity. Since T{sub}s reflects the evaporative cooling that occurs due to transpiration, the hypothesis that it represents a wet bulb temperature is tested. Mean absolute difference between measured and theoretically derived surface temperature was 0.79℃ and maximum relative error less than 10, which supports the validity of this assumption when dealing with fully watered crops. Surface temperature was then used to estimate short-time crop evapotranspiration using a form of the combination equation first presented by Slatyer and McIlroy (1961). With mean relative errors less than 15, this approach is fairly accurate and thus can be considered as an alternative to other methods of estimating latent heat flux using radiometric surface temperature.
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