Determination of Soil Phase-transition Temperatures in the QLB-NET

作者：Hongjing Cui, Linna Chai, Zongyi Jin, Shaojie Zhao, Xiaoci Wang · 年份：2025 · DOI：10.1109/igarss55030.2025.11242699 · 被引用次数：1 · 研究领域：Climate change and permafrost、Soil Moisture and Remote Sensing、Geothermal Energy Systems and Applications

Soil phase-transition temperature (PTT) is a crucial parameter for accurately determining the soil freeze-thaw (FT) state, which is essential for developing surface FT state identification algorithms based on remote sensing technology and for reliably validating FT products. In this study, the PTT is calculated by applying a sigmoid curve fitting (SCF) method to the relationship between soil temperature and unfrozen soil water content, both of which were measured in situ from the QLB-NET, a dense soil temperature and soil moisture monitoring network in the Qinghai Lake Basin on the Qinghai–Tibet Plateau. The SCF-derived soil PTT is validated using the AMSR2 near-surface FT dataset, obtained through a discriminant function algorithm. Results show that most soil freezing temperatures range from -1°C to 0°C while thawing temperatures fall between -0.5°C and 0.5°C. When the SCF-derived PTT is used as a threshold, the classification accuracy of soil FT states improves significantly compared to a fixed 0°C threshold.