Random Term. AMS Publications. Modify or suggest a term. Glossary History. View source. Overseeding From Glossary of Meteorology. Jump to: navigation , search. A cloud seeding operation in which an excess of nucleating material is released over that required to produce the desired effect. In the case of China, they are likely planning to use smaller amounts of each agent in an effort to cool any moisture in clouds headed for the stadium, forming smaller ice particles that would evaporate before they hit the ground, says Dan Kottlowski, an expert senior meteorologist with weather forecasting service AccuWeather.
Dry ice which is solid carbon dioxide is often used to flash freeze food, and silver iodide a chemical sometimes used in antiseptics has molecular structure very similar to that of ice, allowing the substance to induce freezing when introduced to clouds. Liquid nitrogen is a cryogenic fluid at around — degrees Fahrenheit that can cause rapid freezing on contact with living tissue, which is why it's sometimes used to remove skin lesions such as warts.
This approach could also backfire, however, depending on the amount of the agents used. And the conditions have to be just right for their rain-suppression plan to work.
If the clouds are already too filled with moisture, the Chinese could end up creating what they set out to stop. Most cloud seeding around the world aims at increasing precipitation or suppressing hail, says Joe Golden , a retired senior meteorologist for the National Oceanic and Atmospheric Administration NOAA.
While it is well known that you can overseed, possibly diminishing the chance of precipitation, there have been very few scientific studies documenting this process, says Golden, who managed the last federally sponsored weather modification program in the U. Still, Chinese officials claim to have performed "successful rain elimination" during the Olympics held in Beijing, according to the council.
Earlier this year, the Chinese said a cloud-seeding program directly caused a snowstorm in Hebei , the northeastern province surrounding Beijing. Engineers had blasted some cigarette-size sticks of silver iodide into the sky shortly before the storm. Seeding is also used in the Sierra Mountains of California and in Wyoming to try to increase precipitation in the mountains, thus increasing water levels in reservoirs.
However, he says, there is no proof that this method is successful. The only probable place where cloud seeding could be successful, Alpert says, is when seeding is performed on orographic clouds, which develop over mountains and have a short lifespan.
In this type of cloud, seeding could serve to accelerate the formation of precipitation. Note: Content may be edited for style and length. Science News. The findings were recently reported in Atmospheric Research. Throwing seeds into the wind During the course of his study, Prof. Considering the alternatives Despite being relatively expensive, there are more than 80 cloud seeding projects around the world, according to a recent World Meteorological Organization report.
Reassessment of rain enhancement experiments and operations in Israel including synoptic considerations. Atmospheric Research , ; 97 4 : DOI: ScienceDaily, 1 November
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