Initial Development of a Tactical System for Dispersing Supercooled Stratus

A silver iodide pyrotechnic seeding system was selected for the development of a tactically useful approach to the dispersal of supercooled stratus. Various configurations of the pyrotechnic units were tested for nucleation effectiveness before choosing a 3/4-in diameter unit doped with a small amount of chlorine-bearing compound. The system was field tested in northern Michigan in February of 1977. The tests showed the system capable of producing clearings comparable to those of previous studies using dry ice as a seeding agent. Clearings were produced in clouds as warm as -8 C and as thick as 4000 feet. Targeting the clearings over a predetermined ground location was not especially difficult. While VFR flight conditions and good downward visibility were achieved, visibility on a slanted line-of-sight was poor.