Introduction

The exploratory cloud seeding experiments performed by Langmuir, Schaefer, and Project Cirrus personnel fueled a new era in weather modification research as well as basic research in the microphysics of precipitation processes, cloud dynamics, and small-scale weather systems, in general. At the same time commercial cloud seeding companies sprung up worldwide practicing the art of cloud seeding to enhance and suppress rainfall, dissipate fog, and decrease hail damage. Armed with only rudimentary knowledge of the physics of clouds and the meteorology of small-scale weather systems, these weather modification practitioners sought to alleviate all the symptoms of undesirable weather by prescribing cloud seeding medication. The prevailing view was “cloud seeding is good!”

Scientists were now faced with the major challenge of proving that cloud seeding did indeed result in the enhancement of precipitation or produce some other desired response, as well as unravel the intricate web of physical processes responsible for both natural and artificially stimulated rainfall. We, therefore, entered the era where scientists had to get down in the trenches and sift through every little piece of physical evidence to unravel the mysteries of cloud microphysics and precipitation processes.

As the science of weather modification developed, two schools of cloud seeding methodology emerged. One school embraced what is called the static mode of seeding while the other is called the dynamic mode of seeding.