Performance Characteristics of Various Artificial Ice Nuclei Sources

Abstract

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.