Aerosol effects on Maritime Continent precipitation: Oceanic intensification and land diurnal cycle delay

Abstract Aerosols affect radiation, cloud properties, convection, air temperature, and large-scale circulation, yet their influence on precipitation distribution over the Maritime Continent (MC), a complex tropical region composed of islands interspersed with shallow seas, remains poorly understood. Using high-resolution cloud-system resolving model simulations, satellite observations, and reanalysis data, we demonstrate that rising aerosol concentrations amplify oceanic precipitation more than they suppress land precipitation, thereby increasing the sea-to-land precipitation ratio over the MC. This shift is supported by observations and contrasts with the land-enhanced precipitation distribution seen in pristine simulations or those without aerosol radiative effects. Our results underscore that aerosol-induced radiative cooling stabilizes the lower troposphere more over land than over the ocean, enhancing low-level convergence and convection over the sea. Moreover, high aerosol concentrations delay the diurnal precipitation peak over land from late afternoon to midnight, driven by diminished daytime heating and subsequent nighttime increases in moist static energy—an interesting pattern evident in some observed high-aerosol days.