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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4.2.15 Capped Columns (CPla)

Our aircraft observations indicate that capped columns usually form by

cold region columns falling through a region of active plate growth. The

columnar portions of the crystals are typical cold region columns with length

to width ratios of about three. Ground observations also indicated that the

columnar part of the crystal was stubby. Air observations shololed these

crystals had lengths up to 800 lJm. The end plates were often only partially

replicated.

The nature of the capped part of the column was variable. Usually both

ends were capped, but in some cases only one end of the column was capped. The

end plates were not, in general, equal in diameter. Occasionally, riminp was

observed on these crystals and often the end plates collected other particles,

both planar and columnar types. The accretion of particles at the end plates

indicates that the column changed its original orientation to fall with the

larger end plate leading. According to Ono (1969) this occurs when the

diameter of the end plate exceeds the length of the column.

The air observations indicated that capped columns were usually present

as individual crystals, althOUgh occasionally they were observed in aggregates.

However, at the ground, the capped columns were usually parts of aggregates.

Capped columns were observed to suffer fragmentation in the air and this

usually involved the end plates.

4.2.16 Frozen Drops

Air and ground observations indicated that frozen drops seldom made a

large contribution to the total concentration of ice particles in the air.

Those which were present were generally spherical in shape, although sometimes