Entrainment Makes Pollution More Likely to Weaken Deep Convective Updrafts Than Invigorate Them

Are the results of aerosol invigoration studies that neglect entrainment valid for diluted deep convective clouds? We address this question by applying an entraining parcel model, wherein pollution is assumed to increase parcel condensate retention, to soundings from tropical and midlatitude convective environments. Invigoration of 5-10 % and < 2 % is possible in undiluted tropical and midlatitude parcels, respectively, when freezing is rapid because the positive buoyancy contribution from freezing is larger than the negative buoyancy contribution from condensate loading, leading to positive net condensate contribution to buoyancy. However, aerosol-induced weakening is more likely when realistic entrainment rates occur because water losses from entrainment more substantially reduce the latent heating relative to the loading contribution, leading to larger net negative buoyancy contribution from condensates in polluted than in clean parcels. Our results demonstrate that accounting for entrainment is critical in conceptual models of aerosol indirect effects in deep convection