WMOD00317

• Contract/Permit #: 14-06-D-6999
• Project Name: CAWRP
• Title: Cascades Atmosphere Water Resources Program - Volume I
• Prepared For: US Department of the Interior Bureau of Reclaimation
• Date: 7/1/1970
• Weather Modification - Doc Type: Report

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4,2,10 Scrolls (eli)
According to Magono and Lee. scrolls grow only between -8 and -lOoC.
However, Ono (1970) observed scrolls only at temperatures below -220C. Our
aircraft observations indicate that scrolls grow in two distinct temperature

regimes: -8 to -lOoC, and below -19oC. They appeared more commonly at

temperatures below -190C. Further investigations are needed to clarify the

differences between scrolls grown between -8 to -lOoC and below -190C.

Scrolls were commonly found as individual crystals. but were also

observed as aggregates. They were not observed on the ground as individual

crystals, although they could have been hidden in aggregates. Because of the

nature of the continuous particle sampler scrolls were often too long to be

fully replicated. Normally replicated was a portion of the columnar part of

the crystal and one of the ends. Because of the shortness of the columnar

part of the crystal, the scrolls often impacted on their ends. Thus,

measurements of the widths of these crystals were possible. Air observations

indicated that scrolls were wide, ranging in size from 100 ~m to 600 ~m,
However, the shape and size of the scroll part of the crystal varied
considerably from one crystal to another.
The observations indicated that scrolls do not break up readily in the

.air.

4.2.11 Two-branched Crystals (P3a)

Nakaya (1954) observed that two-branched crystals grow in the temperature

range -12 to -170C. Our aircraft observations indicated that two-branched

crystals were usually found in water-saturated conditions at temperatures

between -12 to -170C. These crystals generally were observed as individual