Dynamical regimes of CCN activation in adiabatic air parcels

TL;DR

This paper investigates the complex activation behavior of twilight clouds, revealing new activation states and oscillations through a novel coupled equation approach, enhancing understanding of their role in Earth's energy balance.

Contribution

It introduces a new method solving coupled K"ohler's and supersaturation equations, uncovering previously unknown activation states and oscillatory behaviors in twilight clouds.

Findings

Identification of new activation states in twilight clouds

Prediction of self-sustained oscillations between haze and droplets

Enhanced understanding of cloud formation under weak updrafts

Abstract

Ubiquitous, yet elusive to a complete understanding: Tiny, warm clouds with faint visual signatures play a critical role in Earth's energy balance. These "twilight clouds", as they are sometimes called, form under weak updraft conditions. Their constituent particles exist in a precarious state, teetering between hazy wisps and activated droplets. This delicate thermodynamic balance creates a limited reservoir of supersaturation, which activated droplets readily consume. Our research presents a novel approach, solving coupled equations for particle growth (K\"ohler's equation) and supersaturation change. This reveals previously unconsidered activation states for these clouds. Additionally, the analysis predicts conditions where particles can exhibit self-sustained oscillations between haze and activated droplet states.