WMOD00462

• Contract/Permit #: 87-1999
• Title: Development of Empirical Equations of Ice Crystal Growth Microphysics for Modeling Analysis - Final Report
• Date: 9/1/1988
• Weather Modification - Doc Type: Report

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hygrometer cylinder, a thermometer, with O.lOC accuracy, indicated the dew
point temperature of the fog. From the air temperaure in both the
suspension chamber and the sealed cylinder at the moment of fog
condensation, the Clausius - Clapyron equation gave the vapor density in
both places, and the difference between the densities was the liquid water
content of the fog.
A hot-wire anemometer, which replaced the pitot tube assembly, greatly
improved the measurement of the updraft speed near the crystal in the
suspension tunnel. A small sensor placed in the center of the tunnel near the
ice crystal provided a more accurate setting for the anemometer than that for
the pitot tube assembly since the flow speed was not uniform within the
tunnel.
The improvements in the experimental techniques increased the
accuracy of the determined data set. Furthermore, the longer growth periods
attained in this study made the ice crystal growth data more useful at
temperatures between -3 and -210C. The data set consists of ice crystal mass
and a-axial length after 10, 13, 16 and 19 minutes, c-axiallength after 10, 13
and 19 minutes and terminal fall speed after 7, 13 and 19 minutes of growth.
A few problems remained including irregular shape and thin plates,
which made the measurements of the dimensions, particularly the c-axis,
difficult. However, because of the improvements made in the study and the
sound techniques borrowed from Kowa (1981), the problems are
comparatively insignificant.

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Takahashi and Fukuta ( to be published)
The investigators of this study inherited the techniques and equipment
from the study of Gong and Fukuta (1985) and Kowa (1981), but made a few

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