Spatio-temporal characteristics and multivariate recurrence period of agricultural drought in Northwestern China.

Agricultural drought poses significant challenges to food production and ecosystem sustainability. The evolution of drought and its recurrence period feature are important for drought mitigation and risk management. This study aims to evaluate agricultural drought using the Standardized Soil Moisture Index (SSMI) based on Global Land Data Assimilation System (GLDAS) products, and extract drought variables using a three-dimensional identification method in Northwestern China. Then, the spatiotemporal dynamics and recurrence characteristics of agricultural droughts were evaluated. The results showed that: (1) Study area experienced alternating phases of dry and wet, with intensification in the 1960s and 1990s, and significant humidification post-2000. All four seasons show a wetting trend, while spring exhibited notable humidification trends. (2) Drought intensity and frequency displayed regional variability, agricultural drought in the west part of the study area were high in frequency but low in intensity, while the opposite was true in the east. (3) Agricultural drought exhibited cyclical behavior with dominant periods of 3.5, 6.6, and 13.5 years, reflecting interannual and interdecadal fluctuations. (4) Multivariate joint recurrence periods highlighted significant correlations among drought characteristics, emphasizing the risk of underestimation when considering single variables. These results offer valuable insights for water resources allocation and drought mitigation.