Spatial Representativeness of Soil Moisture Stations and Its Influential Factors at a Global Scale

The spatial representativeness error of in situ soil moisture (SM) is recognized as a major source of uncertainty when validating satellite SM products with a spatial resolution of tens of kilometers. Site underrepresentation is primarily caused by environmental heterogeneity, but their relationship...

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Veröffentlicht in:IEEE transactions on geoscience and remote sensing Jg. 63; S. 1 - 15
Hauptverfasser: Peng, Chenchen, Zeng, Jiangyuan, Chen, Kun-Shan, Ma, Hongliang, Letu, Husi, Zhang, Xiang, Shi, Pengfei, Bi, Haiyun
Format: Journal Article
Sprache:Englisch
Veröffentlicht: New York IEEE 2025
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Schlagworte:
Collocation methods
Correlation coefficient
Correlation coefficients
Environmental factors
Environmental variables
Evaluation
global scale
Heterogeneity
In situ measurement
Laboratories
Land cover
Land surface
Moisture content
Northern Hemisphere
Plant cover
Reliability
Ridges
Satellites
Sea measurements
Sensors
site representativeness
Soil
Soil measurements
Soil moisture
soil moisture (SM)
Soil properties
Soil texture
Spatial discrimination
spatial heterogeneity
Spatial resolution
Surface topography
Texture
validation
Variability
Vegetation
ISSN:0196-2892, 1558-0644
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Zusammenfassung:The spatial representativeness error of in situ soil moisture (SM) is recognized as a major source of uncertainty when validating satellite SM products with a spatial resolution of tens of kilometers. Site underrepresentation is primarily caused by environmental heterogeneity, but their relationship remains poorly understood. Here, we assessed the spatial representativeness of in situ SM from 322 strictly screened stations worldwide relative to coarse-resolution (~0.25°) satellite footprint based on the extended triple collocation (ETC) method. We then evaluated the influence of the heterogeneity of four environmental factors (soil texture, land cover types, elevation, and vegetation coverage) on site representativeness. Moreover, we calculated SM variability within the satellite footprint based on 1-km SM data to explore its relationship with environmental heterogeneity. Results indicate that about 63% of the sites have relatively good spatial representativeness (ETC-derived correlation coefficient <inline-formula> <tex-math notation="LaTeX">\ge 0.7 </tex-math></inline-formula>). Soil texture and land cover exhibit greater heterogeneity across the mid and high latitudes of the Northern Hemisphere. The larger heterogeneity in elevation and vegetation coverage is primarily found in regions with significant ridges and dense vegetation, respectively. Land cover is the major factor influencing the spatial representativeness of SM sites, and the increase in the heterogeneity of land cover enhances SM variability, which negatively impacts site representativeness. The in situ SM can be more representative when the proportion of the land cover type where the site is located is higher or when there are fewer land cover types within the satellite footprint. Moreover, it is found that the newly proposed metric of the similar area ratio of sites, as a measure of land cover heterogeneity, can effectively reflect SM variability. This metric can also serve as a supplementary criterion for selecting representative sites, particularly in situations where sites are sparse and the ETC method is inapplicable. These findings provide useful references for robust evaluation of satellite SM products based on in situ measurements (e.g., in situ SM upscaling and SM site deployment).
Bibliographie:ObjectType-Article-1
SourceType-Scholarly Journals-1
ObjectType-Feature-2
content type line 14
ISSN:0196-2892
1558-0644
DOI:10.1109/TGRS.2024.3523484