Abstract
Accurate continuous daily evapotranspiration (ET) at the field scale is crucial for allocating and managing water resources in irrigation areas, particularly in arid and semi-arid regions. The authors integrated the modified perpendicular drought index (MPDI) as an indicator of water stress into surface energy balance system (SEBS) to improve ET estimation under water-limited conditions. The new approach fed with Chinese satellite HJ-1 (environmental and disaster monitoring and forecasting with a small satellite constellation) images was used to map daily ET on the desert-oasis irrigation fields in the middle of the Heihe River Basin. The outputs, including instantaneous sensible heat flux (H) and daily ET from the MPDI-integrated SEBS and the original SEBS model, were compared with the eddy covariance observations. The results indicate that the MPDI-integrated SEBS significantly improved the surface turbulent fluxes in water-limited regions, especially for sparsely vegetated areas. The new approach only uses one optical satellite data and meteorological data as inputs, providing a considerable operational improvement for ET mapping. Moreover, HJ-1 high-resolution data promised continuous daily ET at the field scale, which helps in understanding the corresponding relationships among field, crop, and water consumption. Such detailed ET information can greatly serve water resources management in the study area as well as other arid and semi-arid regions.
Highlights
Evapotranspiration (ET), the total amount of water evaporation from land and water surface and transpiration by vegetation, is considered to be the most active process in the terrestrial hydrological cycle and the major component of energy and water balance in agricultural systems [1]
Over the past few decades, many RS-based methods have been developed to estimate land surface flux and ET. These approaches can be broadly grouped into four categories: (1) empirical and semi-empirical methods [7,8]; (2) surface energy balance models (SEB) (e.g., the surface energy balance algorithm for land (SEBAL), the surface energy balance system (SEBS) and mapping ET with internalized calibration (METRIC), the two-source energy balance model (TSEB), and the simplified two-source energy balance model (STSEB) [9,10,11,12,13,14]; (3) vegetation index approaches (e.g., vegetation index combined with the Penman-Monteith (PM) method and the Priestley-Taylor (PT) method) [15,16]; (4) data assimilation combined with land surface models and observations [17,18]
To be able to analyze whether integrating modified perpendicular drought index (MPDI) into SEBS via kB−1 improves the sensible heat
Summary
Evapotranspiration (ET), the total amount of water evaporation from land and water surface and transpiration by vegetation, is considered to be the most active process in the terrestrial hydrological cycle and the major component of energy and water balance in agricultural systems [1]. It is a major consumptive use of precipitation and irrigation water on farmland. Over the past few decades, many RS-based methods have been developed to estimate land surface flux and ET. These approaches can be broadly grouped into four categories: (1) empirical and semi-empirical methods [7,8]; (2) surface energy balance models (SEB) (e.g., the surface energy balance algorithm for land (SEBAL), the surface energy balance system (SEBS) and mapping ET with internalized calibration (METRIC), the two-source energy balance model (TSEB), and the simplified two-source energy balance model (STSEB) [9,10,11,12,13,14]; (3) vegetation index approaches (e.g., vegetation index combined with the Penman-Monteith (PM) method and the Priestley-Taylor (PT) method) [15,16];
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