Spatially heterogeneous wetting and climatic drivers of precipitation variability in arid and semi-arid Northwest China since 1960

This study analyzes the spatiotemporal evolution of precipitation across the arid and semi-arid regions of Northwest China from 1960 to 2020, focusing on long-term trends, regional disparities, and climatic drivers. Piecewise linear regression reveals a sharp wetting transition around 2000, characterized by rising precipitation frequency and intensity. However, this trend is spatially heterogeneous. Fuzzy clustering reveals four distinct change patterns that correspond with key geographic subregions. Before 2000, increases were concentrated in the arid Northern Tianshan (NT) and Tarim Basin (TB); after 2000, semi-arid Northeastern Tibetan Plateau (NETP) and Loess Plateau (LP) became dominant contributors. Precipitation become more seasonally balanced, potentially easing drought stress. Yet, extreme precipitation events have intensified, particularly in arid regions, posing escalating risks to the fragile ecosystems. Slow feature analysis isolates dominant low-varying modes, revealing that NT and NETP are primarily influenced by El Niño-Southern Oscillation, with a two-year lag in NETP. LP is modulated by the East Asian summer monsoon. TB is predominantly affected by the Eurasian wave train pattern and equatorial Indian Ocean sea surface temperature anomalies. These results highlight the complex and regionally varied hydroclimatic change across Northwest China, urgently calling for tailored adaptation and water management strategies.