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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- l05 -

slender and stubbier columns were observed. However, JTlost of the stubbier

columns resembled the typical cold region hollow columns.

Our aircraft observations indicated that columns did not reach a limiting

a-axis dimension after a certain c-axis dimension was attained. Data collected

suggests that columns continue to increase in the a-axis dimension, although at

a decreasing rate, as the c-axis dimension increases. Columns with widths of

at least 240 ~m were observed.

4.2.4 Thin hexagonal Plates (PIa)

The aircraft observations confirmed the findings of Ma~ono and Lee (1966)

that hexagonal plates grow between -10 and -20oC.

In the air, hexagonal plates were often observed as part of aggregates,

particularly when the concentrations of plates exceeded a critical value.

Single hexagonal plates were commonly observed. Some adhesion of plates was

. also noted. At ground level most plates were observed as parts of aggregates.

Aircraft observations indicated that many hexagonal plates were not

regular, but had sides of unequal length. Also, many of the plates collected

on the ground were irregular in shape. This irregularity appeared more

noticeable with the larger plates and near the transition temperatures of -10

and -200C. Plates with trapezoidal shapes were commonly observed near these

temperatures. Plates were often quite regular between -12 to -l7oC. In

addition, plates of unusual shape (for example, with extended sides) were

observed and these appeared more commonly near the transition temperatures.

This type of plate growth does not appear to ,have been reported in the

literature.

Thin hexagonal plates ranged in diameter from under 100 ~m to over