Soil Moisture Persistence and Integrated Drought-State Variability in a Semi-Arid Andean Region

Drought persistence and delayed recovery remain major challenges for drought monitoring in semi-arid environments, where precipitation variability interacts with slowly evolving land-surface conditions. Although precipitation-based indicators effectively characterize meteorological drought, they often provide limited information on the persistence and recovery of integrated dry land-surface states. This study investigates soil moisture persistence and coupled drought-state variability in a semi-arid mountainous region of the southern Peruvian Andes using long-term satellite and reanalysis datasets of precipitation (CHIRPS), root-zone soil moisture (ERA5-Land), vegetation conditions (NDVI), and land surface temperature (LST). Soil moisture persistence was characterized using percentile-based metrics, duration analysis, and temporal persistence diagnostics to evaluate the continuity of dry conditions beyond precipitation anomalies. To synthesize hydroclimatic forcing and land-surface variability within a common framework, an Integrated Drought State (IDS) was developed by combining standardized precipitation, soil moisture, vegetation, and thermal indicators into a simplified diagnostic representation of coupled drought-state variability. The results show measurable temporal persistence in soil moisture together with distinct temporal responses in vegetation and surface thermal conditions, indicating that drought-state continuity reflects coupled land-surface behavior beyond precipitation anomalies alone. Persistent thermal anomalies and reduced vegetation activity co-evolve with soil moisture depletion, indicating that land-surface responses adjust more slowly than atmospheric forcing. The IDS captures the coherent temporal evolution of precipitation, soil moisture, vegetation, and surface thermal conditions during prolonged dry periods, providing an integrated representation of drought-state variability across the study region. Overall, the findings emphasize the importance of incorporating slowly varying land-surface conditions, particularly soil moisture persistence, alongside hydroclimatic forcing to improve the interpretation of drought persistence and recovery in semi-arid mountainous environments.