Spatial-temporal dynamics of meteorological and agricultural drought in Northwest China: Propagation, drivers and prediction

Conventional drought studies have predominantly focused on elucidating the temporal-spatial evolution of drought while neglecting research on drought propagation. Various degrees of correspondence exist within the same drought propagation mode. This study utilized the Standardized Precipitation Evapotranspiration Index (SPEI) and Vegetation Condition Index (VCI) to characterize meteorological drought (MD) and agricultural drought (AD). The temporal-spatial characteristics of drought in Northwest China (NWC) from 1982 to 2020 were examined. Subsequently, the interaction between AD and MD was investigated, encompassing correlation, time-lag, propagation characteristics, and primary modes of propagation. Then, the impacts of climate change (CC) and human activities (HA) on AD were individually assessed and quantified. Finally, the probability and return period of drought propagation in different degrees were predicted. The findings reveal that: (1) MD exhibited short duration, high frequency, and low severity, whereas AD was less frequent but endured longer and caused greater harm. In recent 40 years, MD has shown a decrease, while AD has worsened. (2) AD typically lagged behind MD by 1–3 months, with about 33.72 % of regions experiencing a time-lag of approximately 1 month. Generally, AD displayed a positive correlation with MD, although the adverse impact of MD on AD has lessened in the last decade. (3) The primary mode of drought propagation in NWC was “one-to-one,” while in Ningxia, Gansu, and southern Xinjiang, it was “multiple-to-one.” (4) The sensitivity of AD to different climatic environmental factors exhibited noteworthy geographical variations, with SPEI, soil moisture, and maximum temperature exerting a more substantial impact on AD. CC predominantly had a positive contribution with AD, whereas HA exhibited a negative contribution in 54.24 % of the regions. (5) Future MD was projected to mainly consist of light drought, with AD dominated by no, light, and severe drought. AD was more serious in Qinghai, Ningxia and northern Xinjiang. Different degree of MD can easily lead to the same degree or more severe AD. Analyses of the return period of drought revealed that severe AD may have a greater adverse impact on the agricultural development of NWC in the future.