Penman-Monteith reference evapotranspiration. Comparison with daily lysimeter measurements of alfalfa in Egypt
1999
Gaafar, I.
Among the equations for estimating evapotranspiration (ETo), the FAO Penman-Monteith (FAO-PM) is recommended as a standard. There is a clear underestimation under Mediterranean climatic conditions. Then, the objectives of this thesis were (i) to compare the estimated FAO-PM ETo with measured ETo using high-precision weighing-lysimeter, (ii) to check the quality and integrity of both the agro-meteorological station and lysimeter sensors and data and (iii) investigate on one of the major hypothesis not yet tested: the impact of the regional advenction on ETo. The results indicated that the FAO-PM equation underestimated ETo. Moreover, the reason of such ETo underestimation was due to atmospheric stability caused by regional advenction. In fact, the assumption of neutral state, used in derivation of the FAO-PM equation, is invalid under Egyptian conditions.
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