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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signal paths. The first path is a pulse circuit which processes the pulse

signal from the ice crystal counter through a logarithmic amplifier and these

are then recorded on magnetic tape. The second path consists of an

integrating circuit which integrates the pulses and provides a visual

indication of the rate at which ice crystals are detected. This signal is
also recorded.
Initial airborne testing on the B-23 aircraft revealed the need for
extensive light shielding against the effects of ambient light chopping and
reflection from the aircraft propellers. Also, regulation of the power supply
to the arc lamp was found to be necessary. These problems were overcome and

subsequently several flights have been made with highly encouraging results.

The airborne tests have shown that this instrument can count ice

particles in clouds above a certain threshold size (yet to be determined

accurately) but that it does not "see" cloud droplets or even heavy rain.

The device therefore provides a rather dramatic improvement over previous

techniques for detecting ice particles in clouds. The most significant use

of the device so far has been as an aid in determining in real-time the

effects of artificial ice nuclei on increasing the concentrations of ice

particles in clouds.

1.3.5 Electrical Particle Counter

Preliminary work on the development of a device for counting cloud

particles from an aircraft by detecting the electrical charges they

communicate to a metal wire with which they collide was described by Mach

and Hobbs (1969). Further development and airborne testing of this device

has been carried out by Mr. W. Mach of 0UI' research group.