Seeding of Clouds in Tropical Climates

A synopsis of cloud-seeding experiments shows substantial agreement among experimenters that seeding with spray or hygroscopic particles often dissipates small warm clouds but often stimulates convective activity and initiates or increases rainfall from clouds that exceed approximately 4000 ft in depth, increasing precipitation by 50% or more. On the other hand, seeding with dry ice or silver iodide for effect in super-cooled clouds appears to produce a smaller but still considerable precipitation increase. While open to questions of interpretation, the results suggest strongly that present seeding techniques can produce important local rainfall increases at many places and times when water deficits cause loss and hardship.