Variations of precipitation days and amount across the Qilian Mountains, northeastern Tibetan Plateau during 1979–2024 and climatic drivers

Owing to the scarcity of reliable, continuous daily-scale precipitation data, hydrological dynamics in the Qilian Mountains (northeastern Tibetan Plateau) remain poorly understood. We assessed the performance of the China Meteorological Forcing Data v2.0 (CMFD) against meteorological observations in depicting precipitation at daily, monthly, and annual scales, and investigated variations in annual precipitation days and amount, precipitation across different intensities, and their connections to climate indices over period 1979–2024. The CMFD exhibited high accuracy in capturing precipitation variations across multiple temporal scales, achieving a correlation of 0.98 at the monthly scale and 0.54 at the daily scale. Between 1979 and 2024, the CMFD indicated significant increases in both annual precipitation days and total amount, at rates of 4.5 d decade−1 and 13.0 mm decade−1, respectively, through with a clear regional contrast, characterized by increased wetness in the central-western sectors and a trend toward dryness in the east. The increase in light rain days (4.4 d decade−1) dominated the rise in total precipitation days (98%), while light rain amount showed the greatest increase among all intensity categories (10.5 mm decade−1, or 5% decade−1). A positive phase shift of the Atlantic Multidecadal Oscillation (AMO) since the 1980s was associated with increased decadal precipitation, whereas warm ENSO events and a weakened South Asian summer monsoon posed challenges for precipitation increase. The findings provide a valuable basis for understanding regional hydrological cycle, thereby offering scientific support for ecological restoration and water resource management.