EVAPOTRANSPIRATION ESTIMATION FROM INFRARED SURFACE TEMPERATURE. II: THE SURFACE TEMPERATURE AS A WET BULB TEMPERATURE

摘要

Infrared surface temperature (T s ) has been considered a practical approximation of the true aerodynamic temperature (T o ). Once shown that the two temperatures are basically not the same, a new interpretation of T s became a necessity. Since T 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°C 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.