Spatio-temporal evolution characteristics and driving mechanism of soil drought from a perspective of soil moisture

The North China Plain (NCP) is China’s vital grain-producing core and a typical water-scarce region threatened by frequent soil drought under global climate warming and intensive human disturbances. In this study, the 0.1° monthly FLDAS datasets spanning 1982–2024 were adopted to construct the Standardized Soil Moisture Index (SSMI). We systematically analyzed the spatiotemporal variations, seasonal differentiation, extreme drought dynamics and long-term trend persistence of soil drought across the whole NCP and its five sub-regions. The results revealed that: (1) The most serious drought event occurred from July 2002 to November 2002, with September being the driest month and an average SSMI value of –1.33 in the NCP. (2) Anti-persistence dominated the drought situation in most areas, implying that the current trend is likely to reverse in the future. (3) Wavelet coherence analysis indicated strong coupling interactions among soil moisture, soil temperature and air temperature, which dominate drought evolution, while precipitation and evapotranspiration exert stable regulatory effects across monthly, interannual and interdecadal scales. (4) Soil drought severity rises synchronously with the intensification of meteorological drought, with distinct spatial heterogeneity in drought response among sub-regions. The findings provide a theoretical support for agricultural drought early warning, differentiated water resource allocation and regional drought disaster prevention and mitigation.