Abstract
Abstract. We present a model to retrieve actual evapotranspiration (ET) from satellites' vegetation indices (Parameterization of Vegetation Indices for ET estimation model, or PaVI-E) for the eastern Mediterranean (EM) at a spatial resolution of 250 m. The model is based on the empirical relationship between satellites' vegetation indices (normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI) from MODIS) and total annual ET (ETAnnual) estimated at 16 FLUXNET sites, representing a wide range of plant functional types and ETAnnual. Empirical relationships were first examined separately for (a) annual vegetation systems (i.e. croplands and grasslands) and (b) systems with combined annual and perennial vegetation (i.e. woodlands, forests, savannah and shrublands). Vegetation indices explained most of the variance in ETAnnual in those systems (71 % for annuals, and 88 % for combined annual and perennial systems), while adding land surface temperature data in a multiple-variable regression and a modified version of the Temperature and Greenness model did not result in better correlations (p > 0.1). After establishing empirical relationships, PaVI-E was used to retrieve ETAnnual for the EM from 2000 to 2014. Models' estimates were highly correlated (R = 0.92, p < 0.01) with ETAnnual calculated from water catchment balances along rainfall gradient of the EM. They were also comparable to the coarser-resolution ET products of the Land Surface Analysis Satellite Applications Facility (LSA-SAF MSG ETa, 3.1 km) and MODIS (MOD16, 1 km) at 148 EM basins with R of 0.75 and 0.77 and relative biases of 5.2 and −5.2 %, respectively (p < 0.001 for both). In the absence of high-resolution (< 1 km) ET models for the EM the proposed model is expected to contribute to the hydrological study of this region, assisting in water resource management, which is one of the most valuable resources of this region.
Highlights
IntroductionIts assessment at global and regional scales is essential for forecasting future atmospheric feedback (Jung et al, 2010; Oki and Kanae, 2006; Zemp et al, 2014)
Actual evapotranspiration (ET) is a primary component of the global water cycle
Satellite-based ET models are classified into two categories: (1) empirical, using the relationship between in situ ET and satellite-derived vegetation indices (VIs) (Glenn et al, 2011; Nagler et al, 2012; Tillman et al, 2012), and (2) physical, using surface temperature from satellites to solve energy balance equations (Anderson et al, 2008; Colaizzi et al, 2012)
Summary
Its assessment at global and regional scales is essential for forecasting future atmospheric feedback (Jung et al, 2010; Oki and Kanae, 2006; Zemp et al, 2014). Estimating ET at such scales, is not straightforward and requires the use of models (Chen et al, 2014; Hu et al, 2015; Jung et al, 2009; Trambauer et al, 2014). Data-driven models using satellite information benefit from a continuous spatio-temporal direct observation of the land surface (Ma et al, 2014; Shi and Liang, 2014). Some models combine the two approaches (Tsarouchi et al, 2014)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
