Vapor Growth of Small Ice Crystals at Low Temperatures in an Electrodynamic Levitation Diffusion Chamber

Open Access
Author:
Harrison, Alexander William
Graduate Program:
Meteorology
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 15, 2013
Committee Members:
  • Jerry Y Harrington, Thesis Advisor/Co-Advisor
Keywords:
  • ice
  • ice growth
  • vapor growth
  • vapor deposition
  • kinetically limited
  • laboratory ice growth
  • diffusion chamber
  • KLAH
  • ice model
Abstract:
An experimental Button Electrode Levitation (BEL) diffusion chamber for the growth of small (15 µm to 100 µm radius) ice crystals has been developed and used to produce new ice crystal growth measurements at temperatures near -30 °C. The use of a diffusion chamber allows for controlled growth in stable conditions for high and low supersaturations over ice ranging from 2% to 25%. The temperature inside the chamber can be determined with relatively high precision (to about 0.1 K); however, determination of the saturation state has greater error (typically around 20% reaching a maximum of 50%). Both the accuracy and the practical use of the device were greatly improved by developing software to automatically track, control, and record the growth of the particles. Mass growth data from the BEL chamber are used to test the traditional capacitance model and the Kinetically Limited Adaptive Habit (KLAH) model. The KLAH model is able to reproduce the shape and magnitude of the laboratory data within measured precision that the universally used capacitance is unable to replicate. The KLAH model was also used to determine the critical supersaturations and their dependence on temperature from -30 °C to -35 °C. Critical supersaturations derived from minimizing the error between the KLAH solutions and the laboratory data compare well with values derived from prior studies. Between -30 °C and -34 °C, the critical supersaturation is typically in the range of 3% to 5%; however, a substantial rise in the critical supersaturation occurs at -35 °C. KLAH predicts the axis-averaged deposition coefficients (α) based on the temperature and critical supersaturation, and these were determined to be below 0.1 for most cases, and as low as 0.004. These results are similar to a number of prior laboratory studies, but are at odds with recent measurements taken in the AIDA chamber. Finally, results from the BEL diffusion chamber suggest that ice particle growth may depend on initial size, as has been postulated. Particles grown in the same BEL chamber environment tend to become more massive if their initial radius is below 9 µm.