NCAR | RAL - Winter Cloud Seeding with Silver Iodide Steps

Enhancing Snowfall
In mountainous regions where the water supply depends on winter snow pack, cloud seeding is a technology that aims to enhance snowfall by dispersing silver iodide (AgI) particles into clouds to form ice and cause, or enhance, snowfall. Cloud seeding may use ground-based generators and/or aircraft to disperse AgI into the clouds.
Differentiating the effects of cloud seeding on precipitation amounts versus those from natural variability is a challenge. Historically, cloud-seeding studies used randomized statistical experiments to assess changes in precipitation between conditions with and without seeding, but statistically significant results have rarely been obtained. This is partly because the impact of seeding is likely small compared to the large natural variability of the weather. Despite these challenges, several notable advances during the last decade are bringing us closer to the capability to quantify the impacts of cloud seeding.