Aerosol Effect on the Mobility of Cloud Droplets

TL;DR

This paper investigates how aerosols influence cloud droplet mobility, introducing effective terminal velocity and its dispersion as key measures, and proposes analytical estimations to predict droplet-collection onset.

Contribution

It introduces effective terminal velocity and its dispersion as new measures for aerosol effects on cloud droplets and develops analytical estimations for predicting droplet-collection processes.

Findings

Effective terminal velocity (eta) quantifies droplet mobility.

Dispersion of eta (sigma_eta) indicates aerosol impact.

Relative dispersion (epsilon_eta) predicts droplet-collection onset.

Abstract

Cloud droplet mobility is referred to here as a measure of the droplets ability to move with ambient air. We claim that an important part of the aerosol effect on convective clouds is driven by changes in droplet mobility. We show that the mass-weighted average droplet terminal velocity, defined here as the effective terminal velocity (eta) and its spread (sigma_eta) serve as direct measures of this effect. Moreover, we develop analytical estimations for eta and sigma_eta to show that changes in the relative dispersion of eta (epsilon_eta = sigma_eta/eta) can serve as a sensitive predictor of the onset of droplet-collection processes.