Antecedent soil moisture controls meteorological-to-agricultural drought triggering thresholds

The transition from meteorological to agricultural drought is critical for agricultural risk management, yet its triggering thresholds remain poorly quantified when antecedent soil moisture is neglected. In this study, we develop an improved framework based on vine copula functions to explicitly incorporate antecedent soil moisture into the estimation of drought triggering thresholds across mainland China. The results show that drought propagation is generally rapid, mostly occurring within three months. Drier antecedent soil moisture leads to higher triggering thresholds, indicating an enhanced likelihood of drought propagation under dry antecedent conditions. Notably, compared to non-cropland areas, croplands consistently exhibit higher thresholds, reflecting their inherent vulnerability to precipitation deficits. Temporally, approximately 70% of the study area exhibits an increasing trend in triggering thresholds, with the drought sensitivity of croplands intensifying at a significantly faster rate than that of natural environments. Furthermore, land-atmosphere coupling is identified as the dominant control on threshold spatial variability, showing strong nonlinear enhancement effects. Overall, this framework provides a more realistic representation of drought propagation processes, offering improved support for operational drought early warning and agricultural risk management.