Warming elevates the risk of rain-on-snow events in the arid region of Northwest China

The study region is the arid Northwest China (ARNC). The arid region of Northwest China (ARNC), a snowmelt-dependent area undergoing rapid climate warming, is increasingly exposed to hydrological risks from shifting precipitation phases and declining snowpack. Among these risks, rain-on-snow (ROS) events have emerged as a critical but understudied hazard. This study utilizes ERA5-Land data from 1951 to 2023 to examine the spatial distribution, seasonal dynamics, long-term trends, and key drivers of ROS days across the ARNC. The aim is to clarify how ROS events evolve in space and time under warming and to quantify their sensitivity to changes in rainfall and snowfall patterns. Our results show that the ARNC experiences an average of 14.93 ROS days per year, predominantly occurring in high-altitude zones between 3.0 and 3.5 km. Seasonal patterns are elevation-dependent: spring ROS events dominate below 3.5 km, while summer ROS events increase above this elevation. Over the past seven decades, the frequency of ROS events has increased significantly, particularly at higher elevations. Rainfall changes exert a stronger influence on ROS dynamics than snowfall changes, with the sensitivity to rainy days being 2.3 times higher than to snow cover days. These findings highlight the intensifying role of ROS events in shaping water availability and hydrological risks in the cryospheric landscapes of Northwest China. • Rain-on-snow (ROS) event are analyzed for 1951–2023 in China’s arid northwest region • A significant increase in ROS days is observed, especially at higher altitudes. • Rainfall changes have a more substantial impact on ROS days than snow changes