This process mimics nature where certain airborne substances, e.g., soil particles have the ability to act as ice-forming nuclei and initiate the freezing process. A secondary effect of this process can occur, wherein the freezing of water droplets releases latent heat of fusion into the cloud. This addition of heat, under the right circumstances, can cause the treated clouds to grow larger and last longer than would have naturally occurred. The first freezing process is often referred to as a static seeding effect, increasing the efficiency of the precipitation process within the seeded cloud volume. The second freezing process, resulting from release of additional heat into the cloud, is often called the dynamic effect, whereby the treated clouds are invigorated, thus processing more moisture.
Nature can produce rainfall from clouds that are warmer than freezing.
Tiny water droplets that form during condensation and define the cloud can grow as they collide with one another within the cloud. Various modeling and research studies have indicated that this type of seeding is effective in continental clouds, but ineffective in maritime clouds. Many detailed studies have been conducted to address these questions. These efforts have ranged from chemistry-focused work to broad ranging environmental investigations. The bottom line is that no significant environmental effects have been observed.