大气气溶胶对华南与华北暖季降水影响的区域差异OA

Aerosol-precipitation interactions remain a major source of uncertainty in regional climate studies,par-ticularly over eastern China,where strong anthropogenic emissions coexist with monsoon circulation.Understanding regional differences in these interactions is essential for clarifying regional water cycle processes and improving climate projections.Based on ERA5 and MERRA-2 reanalysis datasets,this study investigates the spatiotemporal variations in precipitation amount and frequency and their statistical relationships with aerosol opti-cal depth(AOD)over South China and North China during the warm season(April-August)from 2004 to 2024. The results reveal a pronounced spatial contrast in both precipitation and AOD distributions.Precipitation ex-hibits a"more in the south,less in the north"pattern,with South China characterized by frequent and persistent light precipitation,while North China experiences substantially lower total precipitation.In contrast,AOD shows a"higher in the north,lower in the south"distribution.This opposing spatial structure provides a fundamental back-ground for distinct aerosol-precipitation relationships in the two regions.Statistical analyses show that aerosols are negatively correlated with both precipitation amount and frequency in South China,but positively correlated in North China.Compared with precipitation amount,precipitation frequency shows a stronger and more robust re-sponse to AOD,indicating that aerosols primarily influence the occurrence probability of precipitation. Multiple linear regression analysis further demonstrates that,after controlling for vertical velocity,specific humidity,and temperature,aerosols contribute independently to precipitation variability.The additional explained variance is approximately 2.0%in South China and 1.0%in North China,suggesting a stronger aerosol influen-ceunder more humid conditions.To further elucidate the underlying mechanisms,the cloud-surface coupling is ex-amined using a decoupling index.South China is generally characterized by a coupled cloud-surface state,in which the cloud base is close to the boundary layer top.Under high aerosol loading,the decoupling index increa-ses,indicating a transition toward a decoupled state.This shift weakens the vertical transport of moisture and aero-sols from the surface to clouds,thereby suppressing precipitation frequency.In contrast,North China is dominated by a decoupled background state.Increasing aerosol loading is associated with a decrease in the decoupling index,implying enhanced coupling.This adjustment shortens the vertical transport pathway and may facilitate convective initiation,leading to increased precipitation occurrence. Overall,aerosol impacts on precipitation exhibit strong spatial heterogeneity and are jointly modulated by moisture availability and boundary layer structure.These findings highlight the importance of considering cloud-surface coupling when interpreting aerosol-precipitation relationships.Nevertheless,uncertainties remain due to limitations in reanalysis datasets in representing aerosol vertical distributions and cloud microphysical processes.Future studies should incorporate high-resolution observations and cloud-resolving simulations to further elucidate the physical mechanisms of aerosol-precipitation interactions.