Weather modification, or cloud seeding, is the treatment of individual
clouds or storm systems with various inorganic and organic materials
in the hope of achieving an increase in rainfall. Introduction
of such material into a cloud that contains supercooled water,
that is, liquid water colder than zero Celsius, has the aim of
inducing freezing, with the consequent ice particles growing
at the expense of liquid droplets and becoming heavy enough to
fall as rain from clouds that otherwise would produce none.
The data available in cloud were collected in the summer
of 1975 from an experiment to investigate the use of massive
amounts of silver iodide 100 to 1000 grams per cloud) in cloud
seeding to increase rainfall.
In the experiment, which was conducted
in an area of Florida, 24 days were judged suitable for seeding
on the basis that a measured suitability criterion (SNE).