*2.2. Datasets* 2.2.1.InSitu Observations

The in situ SM measurements are acquired from the SM and temperature observation network built by the Chinese Academy of Sciences (CAS) [11]. SM was measured by a Hydra soil moisture sensor and recorded by a CR10X/CR1000/CR3000 data logger, with an accuracy of ±2.5%. Table 1 shows detailed information on the stations used in the study. The elevation of these stations ranges from 4468 m to 5100 m a.s.l and spans about 420 km from north to south. The sites also contain several typical vegetation types of the QTP, including alpine swamp meadows, alpine meadows, and alpine steppes. They could represent the varied permafrost environment on the QTP to some extent. We collected 129 in situ SM data during the thawing season (months July, and August) from 2016 to 2019 at these sites, of which 100 were used for training the model and 29 for validation.

**Table 1.** Information of SM monitoring sites.

