A variety of devices that produce artificial nuclei have been used in weather modification experiments. These fall into two broad classifications, i.e., pyrotechnics and steady-state flame-type generators.
The effectiveness-temperature relationships for these classes were measured and are presented in graphical form. In summary, the steady-state systems are in general one order of magnitude more effective than the pyrotechnics at temperatures below −12C. Above this temperature, the effectiveness of the pryotechnics approaches and in some cases exceeds that of the steady-state systems. These different characteristics can be explained by particle size effects.
Other performance parameters are examined. Air-fuel ratio is one of these since effectiveness varies markedly near the stoichiometric air-fuel ratio for steady-state systems. A system which employs isopropylamine as the AgI carrier is more sensitive to changes in air-fuel ratio than the NaI-acetone AgI carriers. Another important performance parameter is AgI burn rate. In general, the effectiveness of a pyrotechnic decreases rapidly and then levels off as the burn rate increases. This same effect has been observed in steady-state systems.