Agricultural drought risk assessment in Southern Plateau and Hills using multi threshold run theory

Agricultural drought in this study is characterized and assessed using the Standardized Soil Moisture Index (SSMI). Employing run theory with three thresholds, SSMI identifies grid-wise drought events, quantifying them in terms of peak, frequency, duration and intensity. To evaluate SSMI's performance in assessing drought risk, a comparison is made with the Standardized Precipitation Evapotranspiration Index (SPEI). Spatially, frequency aligns with duration for both indices, indicating regions with longer drought events also experience more frequent occurrences. Meteorological droughts in SPH from 1991 to 2020 are found to be more intense, frequent, longer-lasting, but less severe. Spatially heterogeneous drought events are identified by both indices, with SSMI proving a reliable indicator of drought risk, similar to SPEI. Archimedean copula functions reveal high joint occurrences of various drought characteristics, suggesting significant correlations. The results show that the joint occurrences of duration and peak, intensity and frequency, and duration and peak are all high. This insight is crucial for enhancing drought risk management and developing more effective warning systems.