Scientists have determined that about 63 percent of existing soil moisture observation stations globally accurately reflect soil moisture conditions at the satellite pixel scale, according to the Aerospace Information Research Institute (AIR) of the Chinese Academy of Sciences.
Soil moisture is critical for climate systems, hydrology and agriculture. While passive microwave remote sensing is effective for large-scale soil moisture monitoring, it often has low spatial resolution. Ground-based stations offer accurate local measurements but can struggle to represent broader satellite-scale conditions, complicating the validation process, said Zeng Jiangyuan, the leader of the research team.
"We used the Extended Triple Collocation (ETC) method to assess the correlation between ground station data and satellite-scale true soil moisture, thereby avoiding the need for additional field data," he said.
Researchers evaluated the spatial representativeness of 322 soil moisture stations worldwide. The results showed that approximately 63 percent of the stations achieved good spatial representativeness.
The research also revealed that greater surface heterogeneity, influenced by environmental factors such as soil texture, land cover, elevation and vegetation, reduces a station's spatial representativeness, particularly in areas with diverse land cover types. Diverse land cover proved to be the most influential factor.
The study was published in IEEE Transactions on Geoscience and Remote Sensing.
The findings provide a basis for the rational deployment of ground sites and the robust validation of satellite products, thus improving climate monitoring, agricultural planning and water resource management, Zeng said.
