WMOD00576

• Title: Summary of Weather Modification Activities Reported in 1979
• Date: 7/1/1980
• Weather Modification - Doc Type: Report

Purpose of Activity

Table 4 shows that the prepondE!rance of weather modification activities
were to increase precipitation. Seven activities had two purposes -- rain
increase and hail alleviation. 1}wo activities reported that no seeding
had been performed.

Table 4. Purpose of wE~ather modification activities

Purpose CY 1979

Increase precipitation
Alleviate hail
Clear fog
Research/testing

33
7
9
7

Techniques and Apparatus

Table 5 shows that ground-based AgI burnE~rs were used in 41 percent of
the activities in CY 1979. Aircraft were used in 69 percent of the 49
reported projects during the yea.r. Fourteen percent of the activities
used both aircraft and ground-based seeding apparatus. Ground-based
silver iodide (AgI) generators 'for precipitation enhancement were either
pyrotechnic flares, liquid-fuele:d burners with acetone and propane, or the
arc-type. These systems generate AgI smok,e particles which are carried
into the clouds by natural air motions. Other ground equipment included
liquid propane emitted as vapor from masts to suppress fog.

Aircraft were fitted with dispensers or augers and doors or chutes to
disperse pellets of dry ice into fog or clouds. In many activities,
aircraft were equipped with liquid-fueled AgI generators or burners and
with pyrotechnics; the latter could be ejected into clouds or could be
burned in place on the trailing edge of the wing. Another aircrafj:
method used in CY 1979 featured the use of both dry ice and pyrotechnics
for precipitation enhancement.

7