Impacts of urban aerosols and land use on clouds and precipitation in urban and adjacent non-urban areas

This study investigates impacts of urban aerosols and land use on precipitation not only in an urban area but also in an adjacent non-urban area, focusing on a mesoscale convective system in the Seoul metropolitan region, South Korea and using a cloud-system-resolving model. Elevated urban aerosol concentrations in turn elevate concentrations of cloud condensation nuclei, enhancing droplet nucleation and lifting up condensation rates, which intensify updrafts. This leads to increased precipitation in the urban area but reduces very heavy precipitation in the non-urban area by disrupting the moist static energy (MSE) fluxes. Conversely, urban land use weakens the surface latent-heat fluxes, suppressing precipitation in the urban area while enhancing precipitation in the non-urban area also by disrupting the MSE fluxes. These findings underscore the importance of evaluating both urban and adjacent non-urban regions—and of considering the dual roles of aerosols and land-use change—to achieve a comprehensive understanding of how urbanization reshapes regional hydrometeorological processes and precipitation patterns • Urban aerosols intensify urban moderate, heavy and very heavy precipitation. • Urban aerosols weaken suburban (or non-urban) very heavy precipitation. • Urban land use reduces urban moderate, heavy and very heavy rain. • Urban land use boosts suburban light, moderate, heavy and very heavy rain. • Disruptions in moist static energy fluxes link urban and suburban rainfall changes.