Convection-Permitting Projections of Summer Extreme Precipitation Over the Tibetan Plateau

Extreme precipitation is crucial for hydrological cycle and water resources, and has increased over many regions in recent decades. However, simulating and projecting precipitation extremes remain challenging over complex terrains, such as the Tibetan Plateau (TP). In this study, we evaluate the performance of the kilometer-scale (3.3 km) convection-permitting ICON model in simulating summer daily precipitation characteristics and extremes over the TP and project its future changes, focusing on the comparison with coarser-resolution CMIP6 models. ICON reasonably reproduces the observed daily precipitation characteristics, reducing the bias by ~80–95% for dry day frequency and precipitation-event persistence compared to ERA5 and the CMIP6 ensemble, and substantially lowering biases in extreme precipitation. For future projections, both ICON and CMIP6 project qualitatively consistent signals, including increasing extreme precipitation over almost the entire TP and, over the southeastern TP, increasing dry-day frequency and more frequent but shorter precipitation events. Despite consistent signs, ICON suggests an overall drier future over the southeastern TP than CMIP6, characterized by larger increases in dry days, smaller increases in extreme precipitation and event frequency, and a larger reduction in event duration. The systematic drier future in ICON compared to CMIP6 are linked to projected weakened low-level southwesterlies south of the TP, which suppress moisture transport into the interior southeastern TP and thus, reduce both daily and extreme precipitation. As water from southeastern TP affects downstream populations closely, these results are expected to provide more reliable projections for future risk assessments.