Validation of MODIS 16 global terrestrial evapotranspiration products in various climates and land cover types in Asia

Abstract

Evapotranspiration (ET), or the sum of water released to the atmosphere from ground surfaces, intercepts canopy precipitation through evaporation and plant transpiration and is one of the most significant components in the water cycle. In this study, Moderate Resolution Imaging Spectroradiometer (MODIS) 16 global terrestrial ET products were validated at 17 flux tower locations in Asia. Overall, overestimations due to energy balance misclosure distorted the trend of the data at nine locations [r: 0.27-0.82; bias: -21.41-2.38 mm 8-d -1 ; Root Mean Square Error (RMSE): 6.12-21.81 mm 8-d -1 ]. Regardless of variation in the scattering patterns, good agreements between MODIS-based ET and ET measured at the flux towers were observed at five locations (r: 0.50-0.76; bias: -1.42-1.99 mm 8-d -1 ; RMSE: 1.99-8.96 mm 8-d -1 ). Underestimation at one site (r = 0.28, bias = -17.00 mm 8-d -1 , RMSE = 17.41 mm 8-d -1 ) was accompanied by mismatches at two sites (r = 0.12-0.18; bias = -4.19 − -0.04 mm 8-d -1 , RMSE = 5.76-7.66 mm 8-d -1 ). The best performances of the MOD16 ET algorithm were observed at sites with forested land cover, but no substantial differences were found under a variety of climate conditions. This study is the first comprehensive trial to validate global terrestrial MODIS ET in Asia, showing that a MODIS global terrestrial ET product can estimate actual ET with reasonable accuracy. We believe that our results can be used as baseline ET values for satellite image-based ET mapping research in South Korea.

Ecosystem Services and Ecological Restoration in the Northern Shaanxi Loess Plateau, China, in Relation to Climate Fluctuation and Investments in Natural Capital

“…In order to demonstrate the reliability of the ET dataset in our site, we offer the following points. First, the validity of MOD16-ET has been verified on different scales, as has been shown for Asia [73], Korea [74], China [75], Shaanxi Provence [76] and the Wei River Basin [77]. Second, the synergy between NPP and ET, which has been found in our site by Jia et al [33], means that ET can be enhanced with the increases in NPP.…”

Evapotranspiration Mapping in a Heterogeneous Landscape Using Remote Sensing and Global Weather Datasets: Application to the Mara Basin, East Africa

“…Nevertheless, it should be noted that the MOD16-NB is not based on in situ measured weather variables, albeit the only public domain 1-km ET product for the study area. Further, previous validation studies [11,28,[48][49][50] also revealed limitations of the product for certain land-cover classes, climate zones and elevation zones. Yet, such a comparison of ET estimates is useful to shed light on differences on ET estimates due to forcing data, model structure and its parameterization.…”

Calibration of Spatially Distributed Hydrological Processes and Model Parameters in SWAT Using Remote Sensing Data and an Auto-Calibration Procedure: A Case Study in a Vietnamese River Basin

“…Though progressing significantly in the past years and gaining maturity enough for calibration of hydrological models, remote sensing-based ET products still induce various uncertainties, e.g., [72,73,80]. These uncertainties come in various forms, such as from temperature and net radiation [35], and the aerodynamic component [81].…”