Anthropogenic aerosol emissions have substantially perturbed the global hydrological cycle since the Industrial Revolution through both aerosol–radiation interactions and aerosol–cloud interactions. Convective precipitation differs fundamentally from large-scale precipitation in its governing dynamics, spatial and temporal scales, and intensity distribution, and is more closely associated with short-duration heavy rainfall and extreme events. Understanding how anthropogenic aerosols alter convective precipitation is therefore essential. However, previous studies have often relied on coarse-resolution global models or high-resolution regional simulations, limiting either the explicit representation of convection or the assessment of statistically robust responses over broad spatial domains.

Here, we investigate the separate effects of aerosol–radiation interactions, referred to as the aerosol direct effect (ADE), and aerosol–cloud interactions, referred to as the aerosol indirect effect (AIE), on global convective precipitation. We employ the Community Earth System Model with a multiscale modeling framework (CESM-MMF), in which a convection-permitting cloud-resolving model is embedded within each host-model grid column. Four experiments are conducted using preindustrial and present-day aerosol emissions, with aerosol radiative feedbacks either enabled or disabled. Sea surface temperatures are prescribed and large-scale winds are constrained to suppress internal variability and facilitate attribution. Convective systems and their associated precipitation are identified using PyFLEXTRKR.

The results reveal pronounced contrasts between land and ocean and between ADE and AIE. Over land, ADE generally enhances convective precipitation by modifying regional radiative heating and horizontal temperature gradients, thereby strengthening low-level convergence, moisture convergence, upper-level divergence, and ascending motion. In contrast, AIE suppresses land convective precipitation. Increased cloud condensation nuclei produce more numerous and smaller cloud droplets, alter condensate partitioning, reduce parcel buoyancy during ascent, and weaken vertical motion, limiting condensational growth at upper levels. Over the oceans, AIE generally increases convective precipitation during most months, opposite to its land response, whereas the ADE response is more spatially and seasonally heterogeneous. These findings demonstrate that aerosol impacts on convection depend strongly on surface type, background circulation, and the balance between radiative and microphysical adjustments. Although the constrained-wind and prescribed-SST configuration does not reproduce the fully coupled climate response, it provides a useful framework for isolating the mechanisms governing aerosol-induced changes in convective precipitation.