Impacts of Droplet Activation on Fast and Slow Responses in a Coupled Aerosol-Climate Model

Several “activation parameterizations” are available for researchers to use when coupling aerosol models to cloud microphysical schemes in global models. While these schemes often perform adequately in offline simulations, the input parameters supplied by a coupled global model may yield a biased sample of aerosol properties and meteorological conditions. In some situations, this could grossly skew the resulting cloud microphysical properties simulated by the global model. By applying a suite of activation parameterizations to a new coupled aerosol- climate model (including a novel statistical emulation of a detailed parcel model), we assess the model’s sensitivity to the base state cloud droplet number distributions in the context of present day vs pre-industrial aerosol and precursor emissions scenarios by analyzing fast responses. Equilibrium simulations are currently in progress.