Enhanced Springtime Frontal Precipitation in Southern China Induced by Anthropogenic Aerosol Mitigation

Synoptic fronts are most active in the mid-latitudes and are often associated with abrupt temperature changes and heavy precipitation. Over China, frontal activities play a crucial role in springtime rainfall, accounting for more than 40% of total precipitation in southern China. While previous studies have mainly focused on the influences of natural forcing and long-term climate change on frontal systems, the role of anthropogenic aerosols and their rapid impacts remain poorly understood. In this study, we investigate the fast response of frontal activity and associated precipitation over China to variations in anthropogenic aerosols. Observational analyses reveal that, concurrent with China’s sharp decline in anthropogenic emissions over the past two decades, frontal precipitation (FP) in spring has significantly increased over southern China, accompanied by a weak decrease in northern China. Simulations using the Community Earth System Model (CESM) indicate that the past anthropogenic aerosols reductions in China could lead to the similar dipole variation in FP, along with a general consistent change in front frequency and precipitation intensity. The changes in frontal activity are a result of the modified horizontal wet-bulb potential temperature gradient, which strengthens in the south whereas weakens in the north. Further analysis indicates that aerosol reductions lead to an immediate increase in surface solar radiation, disturbing near-surface temperature and its meridional gradient. The resulting circulation anomalies enhance convergence updraft over southern China, thus enhancing atmospheric moisture and favoring FP formation. Under China’s carbon neutrality target by 2060, continued aerosol mitigation is expected to further amplify the meridional displacement of FP, with opposing variations in front frequency and precipitation intensity between southern and northern China. Our results highlight the importance of anthropogenic aerosols in modulating synoptic-scale weather processes and provide new insights into intraseasonal precipitation variability under ongoing climate change and emission mitigation.