The Impact of AgI Ice Nucleus Measurements on the Wyoming Weather Modification Pilot Project

The Wyoming Weather Modification Pilot Project (WWMPP) was a multi-year research program designed to test the efficacy of increasing surface water supplies through winter orographic cloud seeding in Wyoming (Breed et al. 2014). Within that project, ice nucleus measurements were made during several consecutive winter seasons. When surface-based measurements failed to verify consistently the adequate targeting of the silver iodide (AgI) seeding agent in one of the ranges used in the randomized crossover design, airborne measurements were made. These efforts were summarized by Boe et al. (2014). This paper provides a more in-depth look at the surface-based measurements made early in the WWMPP that led to a change in the experimental design, and also compares the transport of AgI aloft with the onset of IN detection at the surface near one grouping of target precipitation gauges in the Medicine Bow Range.