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Title: Evaluation of METRIC-derived ET fluxes over irrigated alfalfa crop in desert conditions using scintillometer measurements

item AL-GAADI, KHALID - King Saud University
item PATIL, VIRUPAKSHAGOWDA - King Saud University
item TOLA, ELKAMIL - King Saud University
item MADUGUNDU, RANGASWAMY - King Saud University
item Gowda, Prasanna

Submitted to: Arabian Journal of Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/7/2016
Publication Date: 5/17/2016
Citation: Al-Gaadi, K., Patil, V., Tola, E., Madugundu, R., Gowda, P. 2016. Evaluation of METRIC-derived ET fluxes over irrigated alfalfa crop in desert conditions using scintillometer measurements. Arabian Journal of Geosciences. 9:441.

Interpretive Summary: Agriculture is the largest consumer of freshwater in the world. Therefore, an accurate estimation of ET is essential for the determination of crop water needs and crop water use efficiency. In this study, the METRIC model was evaluated for its ability estimate evapotranspiration over alfalfa crop in desert conditions. Comparison of METRIC-estimated against observed data indicated that METRIC has the ability to accurately estimate surface energy fluxes and evapotranspiration rates in desert conditions.

Technical Abstract: A field study on a 50-ha alfalfa (Medicago sativa L.) irrigated field was conducted to investigate the performance of the remote sensing (RS) based Mapping EvapoTranspiration at high Resolution with Internalized Calibration (METRIC) model in the estimation of evapotranspiration (ET) under the arid conditions of Saudi Arabia. The METRIC model performance was investigated by comparing the energy fluxes estimated by the model to the output of a surface layer scintillometer (SLS) system installed in the field, given the fact that the SLS is efficient in measuring sensible heat fluxes (H) over vegetative areas. Landsat-8 reflectance data were used as inputs for the METRIC model. Results of the study revealed that the HMETRIC data was strongly correlated with the HSLS data with an R2 value of 0.74 (P > F = 0.0064) and a mean bias error (MBE) of 6.05 W m-2 (6 %). The METRIC model showed a good performance in estimating the hourly latent heat (LE) fluxes compared with SLS data with an R2 value of 0.81 (P > F = 0.0023), an MBE of 24.46 W m-2 (8 %) and a Nash–Sutcliffe efficiency (NSE) of 0.91. Furthermore, the hourly ET was estimated with an MBE and an NSE of 0.036 mm h-1 (8 %) and 1.00, respectively. Compared to the SLS data, the METRIC model was found to generally provide an efficient and an accurate means of energy fluxes estimation; therefore, ET estimation over the studied irrigated alfalfa crop.