Date of Award
2023
Document Type
Open Access Dissertation
Degree Name
Doctor of Philosophy in Physics (PhD)
Administrative Home Department
Department of Physics
Advisor 1
Raymond A. Shaw
Advisor 2
Will Cantrell
Committee Member 1
Tianshu Li
Committee Member 2
Issei Nakamura
Abstract
From the molecular dynamics of water molecules to the global processes that control atmospheric circulation: describing the evolution of atmospheric clouds necessitates physics that spans vast spatial scales. In this work, steps are taken towards connecting the molecular physics of ice-nucleation to the growth and subsequent freezing of cloud droplets in convective cumulus clouds. Motivated by experimental evidence of ice nucleation triggered by agitation and distortion of a water droplet surface, the first study in this dissertation uses molecular dynamics simulations to demonstrate that negative Laplace pressure from a curved water surface leads to heterogeneous ice nucleation at higher temperatures. A linear approximation, dependent on latent heat and the molar volume difference between liquid and ice, provides a reasonable estimate of the increase in freezing temperature with decreasing pressure. In the atmosphere, agitation and curvature of water surfaces is likely to occur when cloud droplets reach large enough sizes to experience droplet collisions or breakup. The second study in this dissertation uses in-situ measurements of developing cumulus to address the prominent theory that mixing of cloudy air with dry air at cloud edges produces larger droplets than those found in the undiluted cloud core. Droplet size distributions measured by the Holographic Detector for Clouds (HOLODEC) during the Secondary Production of Ice in Cumulus Experiment (SPICULE) show that diluted cloud edges consistently contain droplets biased towards larger diameters compared to droplets in the adjacent undiluted updraft. Further investigation is required to identify the physical mechanisms responsible for these observed trends.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 4.0 License.
Recommended Citation
Rosky, Elise, "Large cloud droplets and the initiation of ice by pressure fluctuations: Molecular simulations and airborne in-situ observations", Open Access Dissertation, Michigan Technological University, 2023.
Included in
Atmospheric Sciences Commons, Atomic, Molecular and Optical Physics Commons, Statistical, Nonlinear, and Soft Matter Physics Commons