WMOD00137

• Applicant: J. William Bullock
• Project Name: E. of Colorado Springs Research Project
• Date: 3/15/1978
• Weather Modification - Doc Type: Report

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from cockpit communications interference which was never com-

pletely eliminated. No good data in seeded clouds was ob-

tained. One pass with the particle counter through a piece

of the Schweizer contrail showed that the aircraft contrail

contained in the neighborhood of 1010 particles per meter

of flight path.
It is interesting that 1010 particles per meter is also
the result calculated by Knollenberg (1972) for a twin-
engine jet (NCAR Sabreliner) contrail. The occurrence of
similar orders of magnitude for completely different air-
craft configurations and power plants suggests that there

is some mechanism operating in aircraft exhaust wakes that

results in roughly similar numbers of particles per meter

of flight path independent of aircraft or engine type.

The solar cell signal was subject to the constant rolling

of the smaIl aircraft. At the 10w sun angles experienced

in wintertime in the Colorado area, small angles of roll

produced large variations in the cosine of the zenith angle.

This angle determines the response of the cell to the sun.

From the few passes under contrails and seeded clouds, the

best estimate is that a 5% to 20% decrease in solar power

occurred in the cloud shadow.

(The constant rolling produced

a variation of about 20% in the signal.)

In photographs, visual observations and the time~lapse

movies, the seeded portions of the aircraft contrail were

clearly distinguishable from the unseeded portions. See