Long-term variations in precipitation types (rain, snow, and sleet) on the Tibetan Plateau: Implications for the cryosphere and ecohydrological systems

Changes in precipitation types (rain, snow, sleet) under climate warming will directly affect the stability of cryosphere environments, including permafrost, glaciers, and snow cover, thereby influencing flow processes in eco-hydrological systems. Despite their importance, long-term variations in precipitation types and their impacts on cryospheric and ecohydrological systems remain poorly understood. To address this gap, we simulated changes in precipitation types over the Tibetan Plateau using three physical schemes and three machine learning models, integrating observations with multi-model projections from the Coupled Model Intercomparison Project Phase 6 (CMIP6). Results indicate that CMIP6 models underestimate non-rainfall by 36%, while machine learning models perform strongly in short-term predictions but remain limited in long-term extrapolation under insufficient training data. During the historical period (1980–2014), rainfall dominated total precipitation at 61.9%, followed by snowfall at 36.1% and sleet at 2.0%. Rainfall significantly increased at 8.9 mm per year ( p < 0.05), while snowfall and sleet decreased by 1.6 and 1.0 mm per year, respectively ( p > 0.05). Future projections (2015–2100) suggest a shift toward increasing rainfall of 3.0‒12.7 mm per decade ( p < 0.05). Conversely, snowfall declines by 0.5‒4.9 mm per decade ( p < 0.05), accompanied by an expansion of snow-free areas, while sleet exhibits slight fluctuation with a maximum decrease of only 0.11 mm per decade ( p < 0.05). These changes will potentially increase the mean annual ground temperature by 4.1 °C, concurrent with an increase in vegetation cover. This study provides valuable insights into precipitation type changes and their impacts on cryosphere environments.