Characteristics of drought evolution and response relationships on the Northern Slope of the Tianshan Mountains

The northern slope of the Tianshan Mountains (NSTM). This study examines the spatiotemporal variations of meteorological, hydrological, and agricultural droughts in the NSTM region using long-term historical observations and remote sensing data. The relationship between hydrological and meteorological droughts is analyzed through travel theory, while the influence of meteorological factors on agricultural droughts is assessed via correlation analysis. We also explore the spatial correlations and distribution patterns of meteorological and agricultural droughts in the region. From 1980–2019, the time series of the Standardized Precipitation Evapotranspiration Index (SPEI) at annual and seasonal scales in the NSTM showed an upward trend, indicating a significant alleviation of meteorological droughts. This is further quantified by the increase in the annual SPEI at 22 of the 32 stations and by the marked decrease in average drought duration (from 22.96 months in 1980–1989–10.89 months in 2010–2019) and intensity (from 26.79 to 12.41 months). Light to moderate droughts were more prevalent, whereas severe and extreme drought events were less frequent. The annual average runoff at hydrological control stations also showed a significant upward trend. The Standardized Runoff Index (SRI) notably shifted from drought to wet conditions between 1996 and 2003, following a period of recurring droughts from 1983 to 1996. The mean duration and intensity of hydrological droughts during the study period were 15.72 months and 16.94, respectively. The annual average Vegetation Condition Index (VCI) ranged from 40 to 60, with an average of 51.54, indicating generally mild agricultural drought conditions. Both the annual and seasonal VCI trends showed improvements. The correlation between SPEI6 and VCI was notably strong (0.946), suggesting that agricultural droughts in the NSTM are most sensitive to variations in the 6-month scale of meteorological droughts. Furthermore, the positive correlation between rainfall and VCI was 0.87 in areas of woodland, cultivated land, and grassland. The study indicates that meteorological drought can be transferred to agricultural drought, particularly on the 6-month scale, and this transmission is influenced by a combination of climatic and human factors, such as regional warming and humidification, glacier melting, land cover changes, and irrigation patterns. Explanation: This study calculates the SPEI, SRI, and VCI indices for NSTM to quantify meteorological, hydrological, and agricultural droughts in the study area. Geostatistical methods, spatiotemporal analysis, and run theory were applied to analyze the spatiotemporal variation characteristics of the three types of droughts, as well as to examine the matching events and response processes of different drought types. • High resolution monitoring of multiple drought types over a long time series. • Spatiotemporal patterns of meteorological, hydrological, and agricultural droughts. • Regional and seasonal maps reveal strong spatial and temporal heterogeneity. • Hydrological drought often lags meteorological drought and weakens in magnitude. • Causes and response links among drought types are quantified and compared.