Left to nature, many clouds are highly inefficient precipitators, retaining more than 90 percent of their moisture. By cloud seeding, the precipitation efficiency can be greatly improved. Generally, silver iodide is used in ground generators to produce artificial ice nuclei that form ice crystals. Spreading the nuclei via aircraft is also common. These crystals attract moisture from the surrounding air forming droplets that grow large enough to fall to the ground as snow. Some projects using ground-based silver iodide generators to seed winter storms over mountain areas in the western United States have operated continuously since 1950.
Along with his associate Langmuir, he created a way of experimenting with super-cooled clouds using a deep freeze unit of potential agents (salt, talcum powder, soils, dust and various chemical agents) to stimulate ice crystal growth. The experiment was easily replicated and he explored the temperature gradient to establish the -40°C limit for liquid water. Within the month, Schaefer’s colleague, atmospheric scientist Dr Bernard Vonnegut is credited with discovering another method for “seeding” super-cooled cloud water. Dry ice and silver iodide agents are effective in changing the physical chemistry of super-cooled clouds, thus useful in augmentation of winter snowfall over mountains and under certain conditions and lightning and hail suppression. Minute crystals of silver iodide produced in the form of smoke acts as efficient ice forming nuclei at temperatures below -5°C to produce enormous number of nuclei (1015 per gram of silver iodide). When this smoke is introduced into super-cooled cloud, some ice crystals appear when temperatures fall below -4°C, but its formation rapidly increases with decreasing temperatures. Cloud seeding by silver iodide is done either from ground generators or from airborne generators. Substances other than silver iodide as artificial nuclei are lead iodide, cupric sulphide, cupric oxide, ammonium fluoride, cadmium iodide and iodine. However, all these are not as effective as silver iodide.
King and John H. Dickinson, who gave an account of their experiments under General Dyrenforth. They advised the Board it was not necessary to discuss the importance of this work, because if rain can be produced at will, land values will be raised by 300 percent. They told how they had received an appropriation from Congress and had been conducting experiments in South Dakota, but "the government was too slow, and the western people had become interested, so they were here, with their balloons, power, and other apparatus in Galveston ready to be sent, and now they wanted the citizens of San Antonio to come to the front and help by a kind word and a small subscription." The Board passed a resolution heartily recommending their work to the citizens of San Antonio.
After china saw that it was successful, china launched a full biological assault on the skies. Following the games, china officials admitted that the weather was out of their control and attributed to a 2009 blizzard to their own handy work. This shows that we’re not ready for cloud seeding or any other kind of weather modification. This also is an example of how cloud seeding has long-term effects.
"Rainmaking experiments: progress for the arrangements of carrying on operations", San Antonio Daily-News, April 29, 1892.
"The rainmakers: an important meeting held and arrangements made to experiment", San Antonio Daily Light, November 14, 1892.
"The rainmakers welcomed", The Daily Light, November 15, 1892.