Extreme precipitation dominates the increase in total precipitation over the source region of the Yellow River

Increasing variability in alpine precipitation under global warming threatens water security. In this context, total precipitation in the source region of the Yellow River (SRYR) on the Tibetan Plateau has shown a notable increase throughout recent decades. However, how different precipitation intensities contribute to this increase and the underlying mechanisms remain insufficiently understood. To clarify the processes involved, we integrated station observations with high-resolution precipitation datasets and analyzed the changes from the perspectives of moisture supply and vapor-to-precipitation conversion. The dominant precipitation intensity’s contribution under future scenarios was also investigated. Results show that total precipitation increased by 81.69 mm yr −1 from the pre-period (1982–2001) to the post-period (2002–2018). Among precipitation intensities, extreme precipitation contributed most to this increase (∼72%), followed by heavy (∼21%) and moderate (∼9%) precipitation. Conversely, light precipitation showed a slight decrease (−1.7%). The increase in extreme precipitation was mainly driven (∼79%) by enhanced external moisture transport into the SRYR, which is associated with warmer sea surface conditions over the North Atlantic Ocean. About 13% of the increase resulted from higher conversion efficiency, owing to intensified atmospheric humidity and convection. The remaining ∼8% was attributed to enhanced internal moisture recycling linked to wetter soil, increased net radiation, higher vapor pressure deficit, and vegetation greening. Furthermore, future projections suggest that the contribution of extreme precipitation will exceed 76%, surpassing its historical level. These findings highlight the dominant role of extreme events in shaping future precipitation regimes and provide insights for climate adaptation strategies in alpine regions.