Clouds and Precipitation


How are supercooled droplets used for the purpose of cloud seeding?

Cloud seeding is a method for encouraging rain droplets to form in clouds. An experiment was conducted in 1946 by chemist and meteorologist Vincent Schaefer (1906–1993) and physicist, chemist, and Nobel Laureate Irving Languir (1881–1957) in which dry ice (frozen carbon dioxide) at –109°F (-78°C) was placed inside a cloud chamber containing cloud droplets chilled to –40°F (-40°C). The result was that rain droplets formed. The next step was to conduct the experiment in a real-life situation. In the winter of 1946, Schaeffer and Languir had dry ice placed in an airplane, which then dumped the load into a bank of stratocumulus clouds. They were pleased to see success when the dry ice caused a snow flurry to develop.

American physicist Bernard Vonnegut (1914–1997), who also worked with Schaefer, later experimented with other chemicals to see what else would be an effective way to seed clouds. He found that silver iodide, which is still used today, could perform the task well. Since then, other substances have been used to seed clouds, including sea salt and even water droplets. However, all these methods appear to work best in the winter. During warmer months, seeding clouds has proved to be more problematic because the correct conditions to produce precipitation are less common.


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