12 Apr 2023
 | 12 Apr 2023

Deposition freezing, pore condensation freezing and adsorption: three processes one description?

Maria Lbadaoui-Darvas, Ari Laaksonen, and Athanasios Nenes

Abstract. Heterogeneous ice nucleation impacts the hydrological cycle and climate through affecting cloud microphyiscal state and radiative properties. Despite decades of research, a quantitative description and understanding of heterogeneous ice nucleation remains elusive. Parameterizations are either fully empirical or heavily rely on classical nucleation theory (CNT), which does not consider molecular level properties of the ice nucleating particles - which can alter ice nucleation rates by orders of magnitude through impacting pre-critical stages of ice nucleation. The Adsorption Nucleation Theory (ANT) of heterogeneous droplet nucleation has the potential to remedy this caveat and provide quantitative expressions in particular for heterogeneous freezing in the deposition mode (the existence of which has even been questioned recently). In this paper we use molecular simulations to understand the mechanism of deposition freezing and compare it with pore condensation freezing and adsorption. We put forward the plausibility of extending the ANT framework to ice nucleation (using black carbon as a case study) based on the following findings: i) The quasi-liquid layer at the free surface of the adsorbed droplet remains practically intact throughout the entire adsorption and freezing process, therefore the attachment of further water vapor to the growing ice particles occurs through a disordered phase, similar to liquid water adsorption. ii) The interaction energies that determine the input parameters of ANT (the parameters of the adsorption isotherm) are not strongly impacted by the phase state of the adsorbed phase. Thus, not only the extension of ANT to the treatment of ice nucleation is possible, but the input parameters are also potentially transferable across phase states of the nucleating phase.

Maria Lbadaoui-Darvas et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-644', Anonymous Referee #1, 05 May 2023
  • RC2: 'Comment on egusphere-2023-644', Anonymous Referee #2, 18 May 2023
  • CC1: 'Comment on Lbadaoui-Darvas et al.', Claudia Marcolli, 23 May 2023

Maria Lbadaoui-Darvas et al.

Maria Lbadaoui-Darvas et al.


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Short summary
Heterogeneous ice nucleation is the main ice formation mechanism in clouds. The mechanism of different freezing modes is to date unknown, which results in large model biases. Experiments do not allow for direct observation of ice nucleation at its native resolution. This work uses first principles molecular simulations to determine the mechanism of the least understood ice nucleation mode and link it to adsorption through a novel modelling framework that unites ice and droplet formation.