Spatiotemporal variability and dominant driving factors of satellite observed global soil moisture from 2001 to 2020

Soil moisture is a critical component of the global land-surface hydrological cycle, significantly impacting fields such as meteorology, agriculture, and water resource management. Understanding the spatiotemporal variability of global soil moisture and its dominant driving factors is essential for addressing global climate change and mitigating extreme climate events. This study investigates the spatiotemporal variability of the latest version of the satellite-based global soil moisture (ESA CCI v09.1) and its dominant driving factors across different temporal scales from 2001 to 2020. The results reveal that short-term scales (8-day and monthly) show higher variability, reflecting rapid climate events and soil responses, while long-term scale (annual) demonstrates more stable patterns. On an annual scale, over 5% of the global land area experienced significant drying, while another 5% showed increased wetness. Significant spatial differences in soil moisture were observed across various climate zones and latitudes. Using the Generalized Additive Model, the dominant factors influencing soil moisture trends were identified for each grid. On an 8-day scale, vapor pressure deficit is the primary driver factor in most regions, while evapotranspiration plays a key role in tropical areas. At the monthly scale, vapor pressure deficit influences high latitude regions, whereas precipitation is the main factor at low latitudes. The combined effect of dominant factors on soil moisture is stronger in low latitudes and weaker in high latitudes. These findings improve our understanding of soil moisture dynamics and offer valuable insights for managing water resources and mitigating the impacts of extreme climate events.