A BUTTON-ELECTRODE LEVITATION CHAMBER FOR THE STUDY OF ICE CRYSTAL GROWTH UNDER ATMOSPHERIC CONDITIONS

Open Access
Author:
Davis, Ethan Anthony
Graduate Program:
Meteorology
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
None
Committee Members:
  • Jerry Y Harrington, Thesis Advisor
Keywords:
  • levitation
  • ice crystals
  • electrodynamic levitation
  • meteorology
  • ice
  • crystal growth
Abstract:
The particle-averaged deposition coefficient of ice (α) influences the evolution of cloud microphysics, cloud structure, and cloud dynamics (Lin et al., 2002; Gierens et al., 2003; Kay and Wood, 2008; Harrington et al., 2009), yet most models assume a deposition coefficient of unity. The deposition coefficient of ice remains relatively uncharacterized over the broad ranges of temperature and supersaturation characteristic of atmospheric clouds. Early laboratory studies provide values of the deposition coefficient that range from 0.001 to 1 at temperatures of 0 to -100 ℃ (Haynes et al., 1992; Pruppacher and Klett, 1997). More recent studies (Magee et al., 2006) suggest a deposition coefficient of α=0.006±0.0025 at temperatures near -50 ℃. Here we introduce a new Button-Electrode Levitation (BEL) device coupled with a parallel plate thermal-gradient diffusion chamber to achieve electrodynamic levitation and growth of small (r≅10-30 μm) ice crystals. The lack of a supporting substrate ensures that the particle growth depends only on the surface properties of ice. By controlling the temperature difference between two ice-coated copper plates, a wide range of temperature and supersaturation is achieved. Commercially available SNOMAX is added to pure water at ∼0.174 g/l to aid in nucleation at higher temperatures and the growth of levitated ice crystals is observed at temperatures as low as -70 ℃.