Cloud seeding, a form of weather modification, is the attempt to change the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud. The usual intent is to increase precipitation (rain or snow), but hail and fog suppression are also widely practiced in airports.
Particles such as silver oxide are sprayed onto clouds to increase precipitation – is commonly used by drought-prone countries, and was part of the Chinese government’s efforts to reduce pollution ahead of the Beijing Olympics in 2008. Other proponents of the “chem-trails” theory say it is an attempt to control global warming, while some cite far more sinister goals, such as population control and military weapons testing.
Cloud seeding also occurs due to ice nucleators in nature, most of which are bacterial in origin
CLOUD SEEDING CAN BE DONE BY GROUND GENERATORS, PLANE, OR ROCKET
The most common chemicals used for cloud seeding include silver iodide, potassium iodide and dry ice (solid carbon dioxide). Liquid propane, which expands into a gas, has also been used. This can produce ice crystals at higher temperatures than silver iodide. After promising research, the use of hygroscopic materials, such as table salt, is becoming more popular. Cloud seeding to in
crease snowfall takes place when temperatures within the clouds are between 19 and −4 °F (−7 and −20 °C). Introduction of a substance such as silver iodide, which has a crystalline structure similar to that of ice, will induce freezing nucleation.
This image explaining cloud seeding shows the chemical either silver iodide or dry ice being dumped onto the cloud, which then becomes a rain shower. The process shown in the upper-right is what is happening in the cloud and the process of condensation to the introduced chemicals. The photo image to the right shows personnel footage of cloud seeding leading to intense flash flooding.