Journal
REMOTE SENSING
Volume 9, Issue 6, Pages -Publisher
MDPI
DOI: 10.3390/rs9060611
Keywords
semiarid areas; Priestley-Taylor coefficient; sensitivity analysis; Landsat; actual evapotranspiration; irrigation water applied; Spain
Categories
Funding
- REDSIM Remote-Sensing based DSS for Sustainable Drought-Adapted Irrigation Management REDSIM
- SIRRIMED Sustainable Use of Irrigation Water in the Mediterranean Region
- HYDROCLIM [CGL2012-39895-C02-01]
- National Plan of R&D of National Secretary of Research, Science and Technology of MINECO (Spain)
- R&D Group of Water Resources Management-UPCT
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This work discusses an operational method for actual evapotranspiration (ET) retrieval from remote sensing, considering a minimum quantity of ancillary data. The method consists in a graphical approach based on the Priestley-Taylor (PT) equation, where the dry soil and non-limiting water conditions are defined by land surface temperature (LST) and vegetation index (VI) space, both retrieved from remote sensing. Using ET tower flux measurements and Landsat 5 TM images of an irrigation scheme in southeast Spain, a sensitivity analysis of ET spatial distribution was performed for the period 2009-2011 with respect to: (i) the shape (trapezoidal or rectangular) of the LST-VI space; and (ii) the value of the PT coefficient, . The results from ground truth validation were satisfactory, both shapes providing similar performances in estimating ET, with root mean square error -30 W/m(2) and relative difference similar to 10% with respect to tower-based measurements. Importantly, the best fit with ground data was found for close to 1, a somewhat different value from the commonly used value of 1.27, indicating that substantial error might arise when using the latter value. Overall, our study underlines the importance of a more precise knowledge of the actual value of coefficient when using ET retrieval methods based on the LST-VI space.
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