Abstract:
The upper reaches of the Hanjiang River Basin are vital water sources and agricultural hub in China, making them essential for studying the spatiotemporal variability of precipitation.Understanding these patterns is crucial for regional water resource management, sustainable economic development, and ecological civilization construction.This study utilizes precipitation data from meteorological stations in the upper Hanjiang River Basin and its surrounding areas from 1961 to 2019.Australian National University Spline (ANUSPLIN) interpolation method is applied to expand the station data to a 1 km spatial resolution.The spatiotemporal evolution of precipitation is then analyzed using several methods, including the Mann-Kendall trend test, sliding t-test, Sen′s slope estimator, Ensemble Empirical Mode Decomposition (EEMD), and cloud model analysis.The results indicated that: ① From 1961 to 2019, the annual, spring, and autumn precipitation in the upper reaches of the Hanjiang River Basin exhibited a decreasing trend, with reduction rates of -7.9, -5.5 mm/10 a, and -6.5 mm/10 a, respectively.In contrast, summer and winter precipitation showed an increasing trend, with rates of 3.6 mm/10 a and 0.6 mm/10 a, respectively.② A significant shift in annual precipitation occurred in 1985, marking a general decline and a tendency towards aridification.Summer and winter precipitation underwent shifts in 1977 and 2007, respectively, exhibiting a reversed U-shaped pattern characteristic of "wet to dry" condition.In contrast, spring and autumn precipitation did not display significant shifts but followed a U-shaped pattern, reflecting "dry to wet" variability.③ Precipitation at research different time scales in the basin predominantly followed an interannual cycle.Interannual and winter precipitation showed relatively high decadal contribution rates, while spring and autumn precipitation were more strongly influenced by trend components.④ Precipitation distribution within the basin exhibited significant spatial heterogeneity, with higher precipitation in spring, summer, and autumn, and lower precipitation in winter.The precipitation showed a decreasing trend from south to north.Spatially, 92.8%, 97.9%, and 100.0% of the regions showed a downward trend for annual, spring, and autumn precipitation, respectively.In contrast, 78.0% and 67.8% of the regions showed an upward trend for summer and winter precipitation respectively.⑤ Winter and spring precipitation demonstrated concentrated and stable trends with small fluctuations, whereas summer precipitation was more dispersed and showed lower concentration.Autumn precipitation had the highest super entropy value, indicating the greatest instability in precipitation trends during this season.This study can provide an important scientific basis for basin water resources management, climate adaptation policy formulation and ecological civilization construction.