Aerosol-driven precipitation modification: spatiotemporal heterogeneity in precipitation microphysics and vertical profiles over China's megacity clusters

Abstract. As crucial atmospheric components, aerosols influence precipitation through complex microphysical mechanisms and exhibit spatiotemporal heterogeneity. This study investigates aerosol effects on precipitation vertical profiles and microphysical characteristics across four Chinese urban clusters (the Beijing–Tianjin–Hebei (BTH), Yangtze River Delta (YRD), Yangtze River Middle Reaches (YRM), and Pearl River Delta (PRD)), including sensitivities to meteorological factors. Initially, the principal findings elucidate three fundamental attributes of precipitation differences: regional disparities surpass seasonal variations in magnitude; heightened aerosol loadings mitigate regional precipitation discrepancies, particularly during the spring and summer seasons; convective precipitation exhibits greater regional and seasonal variability than stratiform precipitation. Furthermore, the findings indicate that aerosols exert an influence on precipitation through microphysical processes, encompassing the growth via condensation on cloud condensation nuclei, coalescence growth, semi-direct effect, and moisture competition. These phenomena exhibit distinct variations that are influenced by spatial and temporal factors, along with the particular type of aerosols present. Specifically, convective precipitation in the BTH region is dominated by the semi-direct effect and invigoration effect of dust aerosols, whereas the YRD and PRD are more influenced by hygroscopic sea salt aerosols and the YRM by fine aerosol particles. Furthermore, RH promotes condensation and coalescence processes by replenishing water vapor, particularly under low aerosol loading. However, CAPE plays a dual role: it enhances precipitation by intensifying cloud development and suppresses it through particle break-up driven by dynamics. The present study elucidates the mechanisms of spatio–temporal modulation underlying aerosol–precipitation interactions, offering a scientific foundation for the refinement of climate models within urban agglomerations.