Theory and Experiments Pertaining to Atmospheric Ice Crystal Growth and Surface Evolution
Open Access
Author:
Hanson, Elle Richard
Graduate Program:
Meteorology and Atmospheric Science
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
January 15, 2019
Committee Members:
Jerry Y Harrington, Thesis Advisor/Co-Advisor Matthew Robert Kumjian, Committee Member Miriam Arak Freedman, Committee Member William Henry Brune, Committee Member
From polar ice fogs to tropical cirrus, atmospheric ice is critically important to weather and climate, but our understanding of the vapor depositional growth of atmospheric ice particles still has significant lacunae. Models of ice particle depositional growth rely on many unrealistic assumptions regarding the particle surface characteristics and morphology, and often fail to reproduce experimental measurements of growth rates. All cloud models still rely on the crystal “capacitance” analogy, which is only applies to particles with rough surfaces or sublimating particles. I performed a series of experiments to measure the growth rates of ice crystals.
I describe a series of different ice crystal models from purely diffusive “capacitance” to surface kinetics-based habit evolution methods, focusing on their assumptions, successes, and limitations. I use a simple method to test the ability of models to reproduce growth rates from 45 experiments performed by myself and other researchers. In addition, I modify an existing ice growth model to simulate the formation of facets on a spherical or rough ice particle, and I show that this model is able to correctly simulate an experiment that other models cannot.