The Use of Silver Iodide for Seeding Individual Clouds

The results of seeding thirty-five supercooled clouds, mostly cumuliform, are described. The silver iodide was released as a smoke from aircraft flying through the upper levels of the cloud or just below cloud base. It is concluded that silver iodide is an effective agent in inducing precipitation in clouds whose upper levels are at temperatures colder than —5° C, and that the precipitation is usually released 20 to 25 minutes after seeding in the case of cumulus clouds but later in the case of layer clouds.