Upscaling Evapotranspiration from a Single-Site to Satellite Pixel Scale
It is of great significance for the validation of remotely sensed evapotranspiration (ET) products to solve the spatial-scale mismatch between site observations and remote sensing estimations. To overcome this challenge, this paper proposes a comprehensive framework for obtaining the ground truth ET...
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| Format: | Article |
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MDPI AG
2021-10-01
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| Series: | Remote Sensing |
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| Online Access: | https://www.mdpi.com/2072-4292/13/20/4072 |
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| author | Xiang Li Shaomin Liu Xiaofan Yang Yanfei Ma Xinlei He Ziwei Xu Tongren Xu Lisheng Song Yuan Zhang Xiao Hu Qian Ju Xiaodong Zhang |
| author_facet | Xiang Li Shaomin Liu Xiaofan Yang Yanfei Ma Xinlei He Ziwei Xu Tongren Xu Lisheng Song Yuan Zhang Xiao Hu Qian Ju Xiaodong Zhang |
| author_sort | Xiang Li |
| collection | DOAJ |
| description | It is of great significance for the validation of remotely sensed evapotranspiration (ET) products to solve the spatial-scale mismatch between site observations and remote sensing estimations. To overcome this challenge, this paper proposes a comprehensive framework for obtaining the ground truth ET at the satellite pixel scale (1 × 1 km resolution in MODIS satellite imagery). The main idea of this framework is to first quantitatively evaluate the spatial heterogeneity of the land surface, then combine the eddy covariance (EC)-observed ET (ET_EC) to be able to compare and optimize the upscaling methods (among five data-driven and three mechanism-driven methods) through direct validation and cross-validation, and finally use the optimal method to obtain the ground truth ET at the satellite pixel scale. The results showed that the ET_EC was superior over homogeneous underlying surfaces with a root mean square error (RMSE) of 0.34 mm/d. Over moderately and highly heterogeneous underlying surfaces, the Gaussian process regression (GPR) method performed better (the RMSEs were 0.51 mm/d and 0.60 mm/d, respectively). Finally, an integrated method (namely, using the ET_EC for homogeneous surfaces and the GPR method for moderately and highly heterogeneous underlying surfaces) was proposed to obtain the ground truth ET over fifteen typical underlying surfaces in the Heihe River Basin. Furthermore, the uncertainty of ground truth ET was quantitatively evaluated. The results showed that the ground truth ET at the satellite pixel scale is relatively reliable with an uncertainty of 0.02–0.41 mm/d. The upscaling framework proposed in this paper can be used to obtain the ground truth ET at the satellite pixel scale and its uncertainty, and it has great potential to be applied in more regions around the globe for remotely sensed ET products’ validation. |
| first_indexed | 2024-03-10T06:14:18Z |
| format | Article |
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| institution | Directory Open Access Journal |
| issn | 2072-4292 |
| language | English |
| last_indexed | 2024-03-10T06:14:18Z |
| publishDate | 2021-10-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Remote Sensing |
| spelling | doaj.art-6b7ad48ec4c54cf5bf4df5b4cb78f07e2023-11-22T19:53:44ZengMDPI AGRemote Sensing2072-42922021-10-011320407210.3390/rs13204072Upscaling Evapotranspiration from a Single-Site to Satellite Pixel ScaleXiang Li0Shaomin Liu1Xiaofan Yang2Yanfei Ma3Xinlei He4Ziwei Xu5Tongren Xu6Lisheng Song7Yuan Zhang8Xiao Hu9Qian Ju10Xiaodong Zhang11State Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, ChinaState Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, ChinaState Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, ChinaHebei Technology Innovation Center for Remote Sensing Identification of Environmental Change, School of Geography, Hebei Normal University, Shijiazhuang 050024, ChinaState Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, ChinaState Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, ChinaState Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, ChinaSchool of Geographical Sciences, Southwest University, Chongqing 400715, ChinaState Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, ChinaState Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, ChinaState Key Laboratory of Earth Surface Processes and Resource Ecology, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, ChinaShanghai Aerospace Electronic Technology Institute, Shanghai 201109, ChinaIt is of great significance for the validation of remotely sensed evapotranspiration (ET) products to solve the spatial-scale mismatch between site observations and remote sensing estimations. To overcome this challenge, this paper proposes a comprehensive framework for obtaining the ground truth ET at the satellite pixel scale (1 × 1 km resolution in MODIS satellite imagery). The main idea of this framework is to first quantitatively evaluate the spatial heterogeneity of the land surface, then combine the eddy covariance (EC)-observed ET (ET_EC) to be able to compare and optimize the upscaling methods (among five data-driven and three mechanism-driven methods) through direct validation and cross-validation, and finally use the optimal method to obtain the ground truth ET at the satellite pixel scale. The results showed that the ET_EC was superior over homogeneous underlying surfaces with a root mean square error (RMSE) of 0.34 mm/d. Over moderately and highly heterogeneous underlying surfaces, the Gaussian process regression (GPR) method performed better (the RMSEs were 0.51 mm/d and 0.60 mm/d, respectively). Finally, an integrated method (namely, using the ET_EC for homogeneous surfaces and the GPR method for moderately and highly heterogeneous underlying surfaces) was proposed to obtain the ground truth ET over fifteen typical underlying surfaces in the Heihe River Basin. Furthermore, the uncertainty of ground truth ET was quantitatively evaluated. The results showed that the ground truth ET at the satellite pixel scale is relatively reliable with an uncertainty of 0.02–0.41 mm/d. The upscaling framework proposed in this paper can be used to obtain the ground truth ET at the satellite pixel scale and its uncertainty, and it has great potential to be applied in more regions around the globe for remotely sensed ET products’ validation.https://www.mdpi.com/2072-4292/13/20/4072upscaling methodsground truth at the satellite pixel scaleeddy covariance systemuncertainty |
| spellingShingle | Xiang Li Shaomin Liu Xiaofan Yang Yanfei Ma Xinlei He Ziwei Xu Tongren Xu Lisheng Song Yuan Zhang Xiao Hu Qian Ju Xiaodong Zhang Upscaling Evapotranspiration from a Single-Site to Satellite Pixel Scale Remote Sensing upscaling methods ground truth at the satellite pixel scale eddy covariance system uncertainty |
| title | Upscaling Evapotranspiration from a Single-Site to Satellite Pixel Scale |
| title_full | Upscaling Evapotranspiration from a Single-Site to Satellite Pixel Scale |
| title_fullStr | Upscaling Evapotranspiration from a Single-Site to Satellite Pixel Scale |
| title_full_unstemmed | Upscaling Evapotranspiration from a Single-Site to Satellite Pixel Scale |
| title_short | Upscaling Evapotranspiration from a Single-Site to Satellite Pixel Scale |
| title_sort | upscaling evapotranspiration from a single site to satellite pixel scale |
| topic | upscaling methods ground truth at the satellite pixel scale eddy covariance system uncertainty |
| url | https://www.mdpi.com/2072-4292/13/20/4072 |
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