Spatio-Temporal Characteristics of Extreme Precipitation in the Zhangye Region on the Northern Slope of the Qilian Mountains, 1960–2023

Abstract

Based on daily precipitation observations from six national meteorological stations in the Zhangye region from 1960 to 2023, this study examines the spatiotemporal evolution and possible driving factors of extreme precipitation using four ETCCDI-recommended indices (SDII, R10mm, R95p, and RX1day). Trends were evaluated using linear regression and the Mann–Kendall test, with Sen’s slope estimation. The results reveal significant (p < 0.05) increasing trends in both the frequency and intensity of extreme precipitation, with a shift from low-intensity, low-frequency to high-intensity, high-variability modes. Temporally, all indices exhibited a step-like surge around 2000, entering a period of high-level oscillation, with extreme characteristics amplified during strong El Niño years. Spatially, a distinct “higher in the south, lower in the north” pattern prevails among the six stations, with the southern Qilian Mountains being the primary contributor and the central plains showing a bimodal distribution, reflecting joint modulation by westerly troughs and local strong convection. The intensification is linked to enhanced atmospheric water vapor, northward penetration of the East Asian summer monsoon, and topographically forced lifting. While alleviating drought stress, this trend substantially elevates the risk of flash floods and debris flows in mountainous areas. It should be noted that the spatial patterns are derived from six stations and should be interpreted as inter-station comparisons rather than continuous spatial fields.