Experimental Study of Ice Crystal Growth below Water Saturation in the University of Utah Supercooled Cloud Tunnel

Abstract

   The growth parameters of ice crystals as a function of time were experimentally determined under free fall at and below water saturation at temperatures of −10, −15, and −20°C using the University of Utah Supercooled Cloud Tunnel. To stably suspend the ice crystals in the tunnel, various improvements were made including vortex and turbulence suppression.
   Results of the experiments showed that the shapes of ice crystals grown were plate and column, and not dendrite. Their mass and fall velocity after growth of 30 minutes were determined as about 10⁻⁵g and 50 cm/s or less, respectively. The relationships among the fall velocity (v cm/s), the mass (m g), and the maximum dimension (d cm) after 10 min. growth period were obtained as m=1.7×10⁻³ d^1.9 and v=4.8×10³ m^0.38. Application of the results in cloud physics studies and precipitation control is envisaged.