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Remote Sens. 2017, 9(8), 779;

Estimating Daily Reference Evapotranspiration in a Semi-Arid Region Using Remote Sensing Data

Centre for Landscape and Climate Research, School of Geography, Geology and the Environment, University of Leicester, Leicester LE1 7RH, UK
Department of Soil and Water Science, Faculty of Agricultural Sciences, University of Sulaimani, Iraq-Kurdistan Region-Sulaimani-Bekrajo 46011, Iraq
National Centre for Earth Observation, University of Leicester, Leicester LE1 7RH, UK
Author to whom correspondence should be addressed.
Academic Editors: Magaly Koch, Brian F. Thomas, Ahmed Gaber and Prasad S. Thenkabail
Received: 19 May 2017 / Revised: 26 July 2017 / Accepted: 27 July 2017 / Published: 29 July 2017
(This article belongs to the Special Issue Remote Sensing of Arid/Semiarid Lands)
PDF [3345 KB, uploaded 31 July 2017]


Estimating daily evapotranspiration is challenging when ground observation data are not available or scarce. Remote sensing can be used to estimate the meteorological data necessary for calculating reference evapotranspiration ETₒ. Here, we assessed the accuracy of daily ETₒ estimates derived from remote sensing (ETₒ-RS) compared with those derived from four ground-based stations (ETₒ-G) in Kurdistan (Iraq) over the period 2010–2014. Near surface air temperature, relative humidity and cloud cover fraction were derived from the Atmospheric Infrared Sounder/Advanced Microwave Sounding Unit (AIRS/AMSU), and wind speed at 10 m height from MERRA (Modern-Era Retrospective Analysis for Research and Application). Four methods were used to estimate ETₒ: Hargreaves–Samani (HS), Jensen–Haise (JH), McGuinness–Bordne (MB) and the FAO Penman Monteith equation (PM). ETₒ-G (PM) was adopted as the main benchmark. HS underestimated ETₒ by 2%–3% (R2 = 0.86 to 0.90; RMSE = 0.95 to 1.2 mm day−1 at different stations). JH and MB overestimated ETₒ by 8% to 40% (R2= 0.85 to 0.92; RMSE from 1.18 to 2.18 mm day−1). The annual average values of ETₒ estimated using RS data and ground-based data were similar to one another reflecting low bias in daily estimates. They ranged between 1153 and 1893 mm year−1 for ETₒ-G and between 1176 and 1859 mm year−1 for ETₒ-RS for the different stations. Our results suggest that ETₒ-RS (HS) can yield accurate and unbiased ETₒ estimates for semi-arid regions which can be usefully employed in water resources management. View Full-Text
Keywords: reference evapotranspiration (ETₒ); remote sensing; AIRS/AMSU; semi-arid region reference evapotranspiration (ETₒ); remote sensing; AIRS/AMSU; semi-arid region

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Najmaddin, P.M.; Whelan, M.J.; Balzter, H. Estimating Daily Reference Evapotranspiration in a Semi-Arid Region Using Remote Sensing Data. Remote Sens. 2017, 9, 779.

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