Summer Precipitation Long‐Term Changes at Different Intensities in the Beijing–Tianjin–Hebei Region From 1961 to 2014 and Simulation Performance Evaluation of <scp>CMIP6</scp> Models

ABSTRACT Using daily gridded precipitation data from CN05.1 (1961–2014) and 14 high‐resolution CMIP6 (Coupled Model Intercomparison Project Phase 6) historical simulations, this study examines spatiotemporal variations in summer precipitation days across intensity levels in the Beijing–Tianjin–Hebei (BTH) region and evaluates the CMIP6 models' simulation performance. The results indicate that: (1) strong precipitation seasonality, with summer (June–August) accounting for most rainfall (light rain dominates: 50.35% of precipitation, 88.43% of rainy days), decreases from southeast to northwest; (2) light rain days show ‘decreasing–increasing’ patterns, moderate rain exhibits ‘increasing‐decreasing’ trends with reduced intensity, while heavy‐to‐torrential rain generally declines. Spatially, light rain days show marked regional variations across time periods, moderate rain days display a regional ‘increasing–decreasing’ pattern, and heavy‐to‐torrential rain days remain relatively stable. (3) CMIP6 models exhibit differences in simulating precipitation days and intensity across different levels in the BTH region. CMIP6 evaluation reveals EC‐Earth3 and EC‐Earth3‐Veg perform best across intensities. Most CMIP6 models accurately simulate moderate rain days but perform poorer for light and heavy‐to‐torrential rain. However, the best‐performing models' ensemble mean for heavy‐to‐torrential rain shows superior spatial agreement with observations. The multi‐model ensemble mean shows biases: overestimating precipitation amounts while underestimating total and light rain days and overestimating moderate and heavy‐to‐torrential rain days.