Evaluation of sebal and metric based evapotranspiration in arid region of Samail, Oman

Crop water requirement of any crop needs accurate estimation especially, in arid regions where scares water, high temperature and scattered low amount of rain are dominating the climate conditions. Traditional climatological and meteorological point-based methods showed limited capabilities in accurately estimating actual evapotranspiration (ETa) over different scales of covering area. Surface Energy Balance Algorithm for Land (SEBAL) and Mapping EvapoTranspiration at high Resolution with Internalized Calibration (METRIC) models provide primarily applied remote sensing methods to estimate ETa on both, regional and local scale. This study analyzed the performance of both models in arid region of Samail, Oman. Results from the study shown that SEBAL model was overestimating ETa but not significantly, as compared to METRIC and modified Penman-Monteith (PM) models. The difference between ETa values estimated by SEBAL and METRIC was due to difference of calibration of ETa on the daily basis as SEBAL uses total daily Net Radiations (Rn24) and METRIC use cumulative reference evapotranspiration (ETr24). Moreover, METRIC model considered local weather conditions more than SEBAL model. This study concluded that METRIC model can produce ETa maps of high spatial and temporal resolution on local scale for the study area. On the other hand, SEBAL model can be applied on the global scale or in areas with less available metrological details.