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Remote Sens. 2017, 9(2), 104;

Validation Analysis of SMAP and AMSR2 Soil Moisture Products over the United States Using Ground-Based Measurements

Institute of Remote Sensing and Digital Earth, Chinese Academy of Sciences, Beijing 100101, China
School of Earth Science and Resource, China University of Geosciences, Beijing 100083, China
School of Land Science and Technology, China University of Geosciences, Beijing 100083, China
Author to whom correspondence should be addressed.
Academic Editors: José A.M. Demattê, Nicolas Baghdadi and Prasad S. Thenkabail
Received: 10 November 2016 / Revised: 16 January 2017 / Accepted: 23 January 2017 / Published: 25 January 2017
(This article belongs to the Special Issue Remote Sensing Applied to Soils: From Ground to Space)
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Soil moisture products acquired from passive satellite missions have been widely applied in environmental processes. A primary challenge for the use of soil moisture products from passive sensors is their reliability. It is crucial to evaluate the reliability of those products before they can be routinely used at a global scale. In this paper, we evaluated the Soil Moisture Active/Passive (SMAP) and the Advanced Microwave Scanning Radiometer (AMSR2) radiometer soil moisture products against in situ measurements collected from American networks with four statistics, including the mean difference (MD), the root mean squared difference (RMSD), the unbiased root mean square error (ubRMSE) and the correlation coefficient (R). The evaluation results of SMAP and AMSR2 soil moisture products were compared. Moreover, the triple collocation (TC) error model was used to assess the error among AMSR2, SMAP and in situ data. The monthly average and daily AMSR2 and SMAP soil moisture data were analyzed. Different spatial series, temporal series and combined spatial-temporal analysis were carried out. The results reveal that SMAP soil moisture retrievals are generally better than AMSR2 soil moisture data. The remotely sensed retrievals show the best agreement with in situ measurements over the central Great Plains and cultivated crops throughout the year. In particular, SMAP soil moisture data shows a stable pattern for capturing the spatial distribution of surface soil moisture. Further studies are required for better understanding the SMAP soil moisture product. View Full-Text
Keywords: soil moisture; SMAP; in situ; AMSR2; triple collocation (TC); statistics soil moisture; SMAP; in situ; AMSR2; triple collocation (TC); statistics

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Zhang, X.; Zhang, T.; Zhou, P.; Shao, Y.; Gao, S. Validation Analysis of SMAP and AMSR2 Soil Moisture Products over the United States Using Ground-Based Measurements. Remote Sens. 2017, 9, 104.

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