Influence of electrostatic collection on scavenging of submicron-sized aerosols by cloud droplets and raindrops

Abstract

We explicitly calculate the efficiency with which submicron-sized aerosol particles (APs) with a diameter smaller than 0.2 $\mathrm{\mu }\mathrm{m}$ collide with cloud droplets and raindrops in air due to individual and combined, simultaneous action of all ice nucleation and all collection mechanisms, including electrostatic forces caused by electric charges on the cloud drops and APs. Brownian diffusion is a predominant collection mechanism up to the critical diameter of APs, which depends on the value of the coefficient of electrostatic collection $\alpha .$ For larger APs, electroscavenging (ES) is the dominant collection mechanism. When ice nucleation is added to all collection processes, at some moments a larger value of $\alpha$ results in a lower mass of APs in rainwater, but only for $\alpha =1$ and $\alpha =3.$ Ice nucleation lowers the relative AP precipitation mass (RAPM) compared with a numerical experiment when all collection processes are included for almost 7% at the end of integration for $\alpha =7,$ while for all other values of $\alpha$ RAPM increases. $\alpha$ affects the mass more than the number of APs in cloud water when ice nucleation and all collection processes act simultaneously. The greatest scavenging in the air occurs for the largest $\alpha .$ ES significantly affects the mass of APs in precipitation at the end of the integration period, while its influence on the number of APs is not that important. The influence of APs charge distribution and an image charge on RAPM and RAPN is significant. For the RAPN the influence of APs distribution compared to an image charge is more significant. The addition of image force to Coulomb force and APs bipolar charge distribution contributes to RAPM for 3.9% and RAPN for 1.6%.

Copyright © 2023 American Association for Aerosol Research

EDITOR:

• Nicole Riemer

Author contributions

Vladan Vučković: conceptualization, methodology, software, investigation, writing original draft, visualization, and supervision. Dragana Vujović: investigation and writing original draft. Darko Savić: investigation.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research was supported by the Ministry of Education, Science and Technological Development of Serbia under grant 451-03-47/2023-01/200162.