Upscaling evapotranspiration measurements from multi-site to the satellite pixel scale over heterogeneous land surfaces

Liu, Shaomin; Xu, Ziwei; Song, Lisheng; Zhao, Qianyi; Ge, Yong; Xu, Tong; Ma, Yanfei; Zhu, Zhanyuan; Jia, Zhiqian; Zhang, Fen

doi:10.1016/j.agrformet.2016.04.008

Cited by 200 publications

(137 citation statements)

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“…The climate is cold and arid, with a mean annual precipitation, temperature, and potential evapotranspiration of 100-250 mm, approximately 7 • C, and 1200-1800 mm, respectively. Its terrain is flat, and its elevation is approximately 1480 m. The two irrigation districts are key experimental areas of the HiWATER project (see Li et al [38] and Liu et al [39] for details). One major objective of the HiWATER project, namely, the Multi-Scale Observation Experiment on Evapotranspiration (HiWATER-MUSOEXE), is to capture the strong land surface heterogeneities and associated uncertainties within a watershed [3,38,39].…”

Section: Study Areamentioning

confidence: 99%

“…MUSOEXE, a component of HiWATER, was implemented to reveal the spatial heterogeneities of heat and water fluxes by constructing a flux matrix (Figure 1c) from May to September 2012. The matrix includes 17 eddy covariance (EC) systems together with automatic weather stations (AWSs) that were installed in the 5.5 × 5.5 km 2 kernel experimental area (Figure 1c) according to the distribution of crops, shelterbelts, roads, residential areas and canals, as well as according to soil moisture and irrigation status [39]. Among the 17 EC systems, 14 were installed in maize fields, and the other three were located in a residential area (EC4 in Figure 1c), a vegetable field (EC1 in Figure 1c) and an orchard (EC17 in Figure 1c).…”

Section: Ground Observation Datamentioning

confidence: 99%

“…Second, all of the raw data were acquired at 10 HZ and processed using the Edire software package developed by the University of Edinburgh (Edinburgh, UK). The processing steps included spike removal, lag time correction, coordinate rotation (2D rotation), frequency response correction, corrections for density fluctuations (WPL-correction), and averaging to half-hourly fluxes [39,41]. Third, a four-step procedure was performed to control the quality of the EC data; for more details, see [1,2].…”

Section: Ground Observation Datamentioning

confidence: 99%

“…In addition, entropy takes into account the distribution of variable values, and its calculation has a certain dependence on the number of samples. Considering the high cost of the experiments, the datasets of the seventeen EC systems and AWS stations in the 5.5 × 5.5 km 2 kernel experimental area are very valuable [39]. Moreover, the conclusions drawn from the analysis based on the spatial data may be quite preliminary but are important and valuable for future exploration in this area.…”

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confidence: 99%

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Analysis of the Spatial Variability of Land Surface Variables for ET Estimation: Case Study in HiWATER Campaign

Xin

Peng

et al. 2018

Remote Sensing

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Heterogeneity, including the inhomogeneity of landscapes and surface variables, significantly affects the accuracy of evapotranspiration (ET) (or latent heat flux, LE) estimated from remote sensing satellite data. However, most of the current research uses statistical methods in the mixed pixel to correct the ET or LE estimation error, and there is a lack of research from the perspective of the remote sensing model. The method of using frequency distributions or generalized probability density functions (PDFs), which is called the "statistical-dynamical" approach to describe the heterogeneity of land surface characteristics, is a good way to solve the problem. However, in attempting to produce an efficient PDF-based parameterization of remotely sensed ET or LE, first and foremost, it is necessary to systematically understand the variables that are most consistent with the heterogeneity (i.e., variability for a fixed target area or landscape, where the variation in the surface parameter value is primarily concerned with the PDF-based model) of surface turbulence flux. However, the use of PDF alone does not facilitate direct comparisons of the spatial variability of surface variables. To address this issue, the objective of this study is to find an indicator based on PDF to express variability of surface variables. We select the dimensionless or dimensional consistent coefficient of variation (CV), Gini coefficient and entropy to express variability. Based on the analysis of simulated data and field experimental data, we find that entropy is more stable and accurate than the CV and Gini coefficient for expressing the variability of surface variables. In addition, the results of the three methods show that the variability of the leaf area index (LAI) is greater than that of the land surface temperature (LST). Our results provide a suitable method for comparing the variability of different variables.

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Section: Study Areamentioning

confidence: 99%

Section: Ground Observation Datamentioning

confidence: 99%

Section: Ground Observation Datamentioning

confidence: 99%

mentioning

confidence: 99%

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Analysis of the Spatial Variability of Land Surface Variables for ET Estimation: Case Study in HiWATER Campaign

Xin

Peng

et al. 2018

Remote Sensing

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“…As one of most important thematic experiments of the HiWATER, the Multi-Scale Observation Experiment on Evapotranspiration (MUSOEXE) over the Zhangye oasis provided multiscale data sets of meteorological elements and land surface parameters that facilitate the development and validation of ET models over heterogeneous surfaces [58,59]. Figure 1 shows the distribution of flux towers and the land use classifications in the MUSOEXE.…”

Section: Hiwater-musoexe Campaign and Ground-based Measurementsmentioning

confidence: 99%

Intercomparison of Three Two-Source Energy Balance Models for Partitioning Evaporation and Transpiration in Semiarid Climates

et al. 2018

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Evaporation (E) and transpiration (T) information is crucial for precise water resources planning and management in arid and semiarid areas. Two-source energy balance (TSEB) methods based on remotely-sensed land surface temperature provide an important modeling approach for estimating evapotranspiration (ET) and its components of E and T. Approaches for accurate decomposition of the component temperature and E/T partitioning from ET based on TSEB requires careful investigation. In this study, three TSEB models are used: (i) the TSEB model with the Priestley-Taylor equation, i.e., TSEB-PT; (ii) the TSEB model using the Penman-Monteith equation, i.e., TSEB-PM, and (iii) the TSEB using component temperatures derived from vegetation fractional cover and land surface temperature (VFC/LST) space, i.e., TSEB-T C -T S . These models are employed to investigate the impact of component temperature decomposition on E/T partitioning accuracy. Validation was conducted in the large-scale campaign of Heihe Watershed Allied Telemetry Experimental Research-Multi-Scale Observation Experiment on Evapotranspiration (HiWATER-MUSOEXE) in the northwest of China, and results showed that root mean square errors (RMSEs) of latent and sensible heat fluxes were respectively lower than 76 W/m 2 and 50 W/m 2 for all three approaches. Based on the measurements from the stable oxygen and hydrogen isotopes system at the Daman superstation, it was found that all three models slightly overestimated the ratio of E/ET. In addition, discrepancies in E/T partitioning among the three models were observed in the kernel experimental area of MUSOEXE. Further intercomparison indicated that different temperature decomposition methods were responsible for the observed discrepancies in E/T partitioning. The iterative procedure adopted by TSEB-PT and TSEB-PM produced higher LE C and lower T C when compared to TSEB-T C -T S . Overall, this work provides valuable insights into understanding the performances of TSEB models with different temperature decomposition mechanisms over semiarid regions.

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Hydrological Cycle in the Heihe River Basin and Its Implication for Water Resource Management in Endorheic Basins

et al. 2018

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Endorheic basins around the world are suffering from water and ecosystem crisis. To pursue sustainable development, quantifying the hydrological cycle is fundamentally important. However, knowledge gaps exist in how climate change and human activities influence the hydrological cycle in endorheic basins. We used an integrated ecohydrological model, in combination with systematic observations, to analyze the hydrological cycle in the Heihe River Basin, a typical endorheic basin in arid region of China. The water budget was closed for different landscapes, river channel sections, and irrigation districts of the basin from 2001 to 2012. The results showed that climate warming, which has led to greater precipitation, snowmelt, glacier melt, and runoff, is a favorable factor in alleviating water scarcity. Human activities, including ecological water diversion, cropland expansion, and groundwater overexploitation, have both positive and negative effects. The natural oasis ecosystem has been restored considerably, but the overuse of water in midstream and the use of environmental flow for agriculture in downstream have exacerbated the water stress, resulting in unfavorable changes in surface‐ground water interactions and raising concerns regarding how to fairly allocate water resources. Our results suggest that the water resource management in the region should be adjusted to adapt to a changing hydrological cycle, cropland area must be reduced, and the abstraction of groundwater must be controlled. To foster long‐term benefits, water conflicts should be handled from a broad socioeconomic perspective. The findings can provide useful information on endorheic basins to policy makers and stakeholders around the world.

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Upscaling evapotranspiration measurements from multi-site to the satellite pixel scale over heterogeneous land surfaces

Cited by 200 publications

References 40 publications

Analysis of the Spatial Variability of Land Surface Variables for ET Estimation: Case Study in HiWATER Campaign

Analysis of the Spatial Variability of Land Surface Variables for ET Estimation: Case Study in HiWATER Campaign

Intercomparison of Three Two-Source Energy Balance Models for Partitioning Evaporation and Transpiration in Semiarid Climates

Hydrological Cycle in the Heihe River Basin and Its Implication for Water Resource Management in Endorheic Basins

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