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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diameter with an ave~age size of about 3000 ~m, Larger c~ystals than this
were observed on the ground,
Both air and g~ound observations indicated that these crystals may be
readily broken up in the air.
4.2,13 8ide Planes (81), Combinations of 8ide Planes, Bullets and Columns
(83) and Radiating Assemblage of Plates (P7a)
According to Ono (1970), side planes (81) form at temperatures below
-220C. Magono and Lee (1966) indicate that side planes (81) grow at
temperatures between -20 to -25oC and combinations of side plates, bullets,
and columns (83) at temperatures below -250C. The growth region for
radiating assemblage of plates is not mentioned by these workers.
Our aircraft observations confirmed that all these crystal types grew
at temperatures below -l80C and at water saturated conditions. Preliminary

results from ground measurements in this study indicate that cloud tops could

have been warmer than -250C when combinations of side plates, bullets, and

columns (83) were observed on the ground. Taken into account when considering

temperature of the cloud tops was the origin and trajectory of these particles,

Aircraft observations indicated that usually these crystal types occurred as

single crystals but occasionally they were found in aggregates. At the ground

these crystals were usually aggregated.
Side planes (81) were numerous both in the air and on the ground, They

were the most common cold region crystal to reach the surface. Radiating

assemblages of plates were also commonly observed at ground level. Observed

more commonly in the air than on the ground, but least common of all, was the

combination of side planes, bullets, and columns.

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