Calibration and validation of solar radiation-based equations to estimate crop evapotranspiration in a semi-arid climate
Γεώργιος Νικολάου, Damianos Neocleous, Antonio Manes, Evangelini Κιττα
Abstract
Abstract The Abtew and Jensen-Haise solar radiation-based equations were used to estimate evapotranspiration, considering the limited climatic data in many locations. Both equations were proven to successfully predict the potential evapotranspiration (ET O ) compared with the standard Penman–Monteith (PM) method in two Mediterranean countries. Calibration of the constant coefficient k of the Abtew equation showed substantial differences compared to recommended values (1.22 vs. 0.53), with the highest values observed during September (1.46). Validation of ET O measurements using calibrated Abtew equation against the PM method indicated a high correlation coefficient (r 2 = 0.97, RMSE = 0.61). Further, evapotranspiration requirements, using the calibrated empirical equation, were calculated for olives (449 mm) and citrus (807 mm) showing a good agreement with recommended values for dry climate regions. Therefore, the tested equations could be safely used to predict frequencies and doses of irrigation in semi-arid climates, considering limited climatic data availability.