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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Fukuta eliminated the previously mentioned problems of measuring the
flow speed. Thus, the improvements and checks concerning ~he use of the
pitot tube arrangement and hot wire anemometer made the fall velocity data
of Takahashi and Fukuta the most reliable.
Another example of the chronological improvement is the methods
used by Fukuta, et al. (1979), Kowa (1981) and Gong and Fukuta (1985) to
measure the liquid water content. Both Fukuta et al. and Kowa used the
plaster of paris method, which contained some drawbacks, including
uncertainties in determining the efficiency of collecting fog droplets, defining
the exact volume of air passing through the U-shape tube, resolving the
glaciation problem of the plaster of paris, and measuring the change of mass
in a much more massive tube assembly. The hygrometer method introduced
by Gong and Fukuta eliminated these difficulties and probably allowed more
reliable measurements of the liquid water content even though
determination of fog condensation point on the hygrometer presented a new
problem.
Improvements in ice crystal preservation provided another example of
increased reliability of data from more recent experimental studies. Fukuta
(1969) and Ryan et al. (1976) used silicon oil on both the sample dish and the
cover glass and allowed the lighter crystal to rise to the surface of the glass.
Fukuta et al. (1979) and later investigators applied motor oil onto the cover
glass and trapped the heavier crystal at the interface between the two oils for
extended periods of time. By preventing the crystal from reaching the glass
surface, the investigator could melt the crystal more reliably into a spherical
rather than a distorted hemispherical drop and measure the radius more

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