Articles | Volume 24, issue 3
Nonlin. Processes Geophys., 24, 535–542, 2017
Nonlin. Processes Geophys., 24, 535–542, 2017

Research article 05 Sep 2017

Research article | 05 Sep 2017

On the CCN (de)activation nonlinearities

Sylwester Arabas1,2 and Shin-ichiro Shima3 Sylwester Arabas and Shin-ichiro Shima
  • 1Institute of Geophysics, Faculty of Physics, University of Warsaw, Warsaw, Poland
  • 2Chatham Financial Corporation Europe, Cracow, Poland
  • 3Graduate School of Simulation Studies, University of Hyogo, Kobe, Japan

Abstract. We take into consideration the evolution of particle size in a monodisperse aerosol population during activation and deactivation of cloud condensation nuclei (CCN). Our analysis reveals that the system undergoes a saddle-node bifurcation and a cusp catastrophe. The control parameters chosen for the analysis are the relative humidity and the particle concentration. An analytical estimate of the activation timescale is derived through estimation of the time spent in the saddle-node bifurcation bottleneck. Numerical integration of the system coupled with a simple air-parcel cloud model portrays two types of activation/deactivation hystereses: one associated with the kinetic limitations on droplet growth when the system is far from equilibrium, and one occurring close to equilibrium and associated with the cusp catastrophe. We discuss the presented analyses in context of the development of particle-based models of aerosol–cloud interactions in which activation and deactivation impose stringent time-resolution constraints on numerical integration.

Short summary
The paper bridges cloud/aerosol modelling with bifurcation analysis. It identifies two nonlinear peculiarities in the differential equations describing formation of atmospheric clouds through vapour condensation on a population of aerosol particles. A key finding of the paper is an analytic estimate for the timescale of the process. The study emerged from discussions on the causes of hysteretic behaviour of the system that we observed in the results of numerical simulations.