Evidence of Dynamic Effects in Cloud Seeding Experiments in South Dakota

Abstract

Silver iodide seeding of convective clouds in a number of experiments in South Dakota has yielded mixed results, including both increases and decreases in rainfall and, apparently, decreases in hail. The results vary with the synoptic situation and with location with respect to the silver iodide release point; there is tentative evidence that they can extend upwind. Two dynamic effects of seeding are postulated, namely, increased growth of seeded clouds and the suppression of neighboring clouds at distances of some tens of miles.