Ion-Induced Cloud Modulation through New Particle Formation and Runaway Cloud Condensation Nuclei Production

A central component of the climate is the coupled aerosol-cloud-precipitation system and its interaction with boundary layer structure and turbulence. The problem of marine cloud brightening in particular begs for a better understanding of aerosol-cloud interactions, including feedback on the sources and properties of those aerosols. This presentation covers a process study of the impact of new particle formation through ionization in clouds and its implications for a potentially new approach to cloud modulation inspired by nature.

We formed cloud in the Pi Convection--Cloud Chamber via ionization in humid conditions, without the injection of aerosol particles to serve as cloud condensation nuclei (CCN). Abundant ions, precursor gases, turbulence, and supersaturated water vapor combine to produce new particles, which grow to become CCN sized and eventually are activated to form clouds. Coupling between the new particle formation and cloud droplets causes predator-prey-type oscillations in aerosol and droplet concentrations under turbulent conditions. Leading terms are identified in the budgets for Aitken and accumulation mode aerosols and for cloud droplets. The cloud coupling is proposed to be a result of cloud-induced runaway CCN production through aerosol scavenging. The experiments suggest potential applications to marine cloud brightening, in which ions rather than sea-salt aerosols are generated.

Reference: K. K. Chandrakar, W. Cantrell, and R. A. Shaw Ion-induced Cloud Modulation Through New Particle Formation and Runaway Cloud Condensation Nuclei Production. Oxford Open Climate Change, 2024 (under review).