New Droplet Nucleation Scheme to Improve Representation of Droplet Concentration and Relative Dispersion

Activation of aerosol particles into cloud droplets (droplet nucleation) is essential to investigating aerosol-cloud interactions and aerosol indirect effects in climate models, and a number of parameterization schemes have been developed. Despite the great efforts, deficiencies remain in existing parameterizations, especially for the updraft-limited regime in which existing parameterizations suffer from the largest uncertainty and lack of representation of relative dispersion. This work presents a new parameterization that aims to fix these deficiencies, with two main tasks. First we will present a “universal” formulation that permits existing parameterizations for droplet concentration to consider relative dispersion and improves the accuracies of these parameterizations, esp., in updraft-limited regime. Second, we will couple the new formulation with commonly used parameterization schemes, and evaluate their performance against detailed parcel model simulations. The resultant new parameterization will improve representation of droplet concentration and relative dispersion from aerosol-limited regime to updraft-limited regime, and allow for exploration of the compensating effects of droplet concentration and relative dispersion in quantification of aerosol indirect effect in climate models.