Cloud seeding is based on the principle of Tor Bergeron called the Bergeron Process. Bergeron is a famous meteorologist who discovered this ingenious method through two specific properties of water; first - that water in the atmosphere does not solidify at 0 degrees centigrade but at -40 degrees centigrade instead. This super cooled water (-40 degrees centigrade) solidifies only when stirred or when it comes in contact with solid particles. And the second property is that vapor pressure saturation of crystals in liquid form is lower than that of the super cooled water.
It was in 1946; however, that Vincent J, Schaefer, a scientists found out that when a solid, freezing particle like dry ice or silver iodide is added to the super cooled clouds, this facilitates the growth of the crystals, large enough to fall as precipitation or rain..
For a successful cloud seeding to occur there are two conditions that should be present; a cloud formation and a topmost portion of this should be able to be super cooled.
The introduction of dry ice or sliver iodide by a plane or from the ground with the use of burners would trigger the initiation of the process.
There are two general types of cloud seeding:
Cumulus clouds are targeted for this type of seeding. This is because they have insufficient freezing nuclei and when this is added artificially, this will enhance precipitation or rainfall.
Massive seeding is utilized where dry ice or silver iodide is rapidly introduced into the clouds. This will then increase the cloud size causing precipitation or rainfall.
Between the two static seeding is more common, which is preferably done on mountain slopes where snow could be melted too when the rain falls after seeding. This would increase the amount of water going down into the lowlands which can be used for agricultural purposes or for power generation.
It is not as simple as it may sound however as there are certain factors that affect cloud seeding. The varied nature and type of clouds affect the procedure significantly.
There were several experiments conducted within the years, some were successful some were dismal failures.
During five summers in 1970, the Florida Cumulus Experiment (FACE) conducted cloud seeding experiments. The initial results were positive but when more specific experiments were done, they were not validated.
Colorado, on the other hand, has been in the cloud seeding program or Weather Modification Program (WM) since the 1950s, and recognizes the significance of the continuous experimentation of the process. Recently after the 2000 drought, permits were awarded to several parts of the state to participate in this program.
These permits were governed by statutes which were promulgated to oversee the proper performance of the procedure.
Cloud seeding is man's artificial way to create rainfall. Perhaps in the near future, we would also be capable of producing clouds? It is a possibility that could be explored.
Whatever benefits we could gain from cloud seeding, these should be weighed against potential hazardous effects. We should only tamper with nature when there are no natural means to solve our problems. It is always safe to do it cautiously, because when nature extracts vengeance, it is without mercy!