State Dependence of Soil‐Moisture Responses to Meteorological Dry–Wet Abrupt Alternation

ABSTRACT Meteorological dry–wet abrupt alternation (M‐DWAA) is an important compound climate extreme that can impose complex stresses on agricultural and ecological systems through rapid shifts between water deficit and excess moisture. Its impacts on land‐surface and ecosystem processes depend partly on whether and how meteorological signals are transmitted into soil moisture. However, the different types of soil‐moisture responses to M‐DWAA and the factors associated with their variability remain poorly understood. Here, global M‐DWAA events during 2001–2023 were identified using the Standardized Precipitation Evapotranspiration Index (SPEI), and corresponding soil‐moisture responses were classified based on whether Standardized Soil Moisture Index (SSMI) anomalies exceeded predefined dry and wet response thresholds during different phases of M‐DWAA events. Random Forest models were further employed to evaluate the relative importance of factors associated with different soil‐moisture response types. The results show that the propagation of M‐DWAA signals into soil moisture was selective. Soil‐moisture responses during both dry and wet phases occurred in only 37.77% of M‐DWAA events, whereas more than half (54.05%) produced responses during only one phase. Moreover, soil‐moisture response patterns were strongly state‐dependent. Dual‐phase responses were generally associated with stronger atmospheric forcing and antecedent soil‐moisture conditions closer to neutral states. Random Forest analysis further identified antecedent soil moisture as the most important predictor, with hydroclimatic and land‐surface conditions providing additional explanatory information. These findings suggest that soil moisture exhibits state‐dependent filtering characteristics, which are associated with differences in how atmospheric dry–wet signals are expressed in terrestrial ecosystems, rather than responding uniformly to atmospheric forcing. This study provides a global perspective for understanding heterogeneous land‐surface responses and assessing ecosystem vulnerability and agricultural water availability risks under increasing climate variability.