Drying–Wetting Changes of Surface Soil Moisture and the Influencing Factors in Permafrost Regions of the Qinghai-Tibet Plateau, China

Soil moisture (SM), an important variable in water conversion between the atmosphere and terrestrial ecosystems, plays a crucial role ecological processes evolution of ecosystems. Analyzing exploring SM’s influencing factors different permafrost regions Qinghai-Tibet Plateau (QTP) can better serve regional security, disaster warning, management, etc. However, changes future trends SM on QTP recent decades are uncertain, main affecting not fully understood. The study used observations, Global Land Evapotranspiration Amsterdam Model (GLEAM) products, meteorological vegetation data, Mann–Kendall test, Theil–Sen estimation, Ensemble Empirical Mode Decomposition (EEMD), correlation methods to analyze explore characteristics change QTP. results show that: (1) At pixel scale, GLEAM products reflect warm season. seasonal region is closer real than permanent region, with median coefficient (R) 0.738, bias 0.043 m3 m−3, unbiased root mean square errors (ubRMSE) 0.031 m−3. (2) average season increased at rate 0.573 × 10−3 m−3 yr−1 over 40 years, trend accelerated from 2005–2020. In 64.31% soil was significantly wetted, mainly distributed which showed that wetting dry faster wet region. does have long-term continuity has pattern “wetting–drying-wetting” interannual decadal levels, especially (3) More 65% caused by temperature, precipitation, vegetation. there apparent spatial heterogeneity cover conditions, three more substantial explanatory power for With global climate change, synergistic SM–Climate–Vegetation effect tends be evident