Deep convection only temporarily intensified by aerosols

Abstract

Whether aerosols invigorate, suppress or have a weak effect on deep convection remains highly debated. Here we investigate how the timescale of aerosol perturbations controls convective responses and show that the apparent invigoration of convection is probably a transient effect. Using cloud-resolving models from a multi-model radiative–convective equilibrium intercomparison project and targeted perturbation experiments, we find that abrupt aerosol increases drive strong convective invigoration, which lasts for about 1 d, but this response vanishes as the environment adjusts and upper-tropospheric warming reduces cloud–environment thermal contrasts. Experiments with oscillating aerosol concentrations confirm this mechanism: rapid aerosol variability can lead to convective invigoration, whereas slow variability yields muted responses. A low-order model further supports the generality of this timescale-dependent framework. These findings highlight that the timescale of aerosol perturbations fundamentally governs their convective impacts—a critical consideration for interpreting both observations and model projections of aerosol–cloud interactions. A sudden rise in aerosols makes clouds more active for about a day. Then the effect fades as the atmosphere adjusts and warms aloft, reducing the contrast that helps clouds grow, according to cloud-resolving model simulations.