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Which substances have been used to seed supercooled clouds?
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weather modification
Cloud seeding can produce an extra 5 to 15% of precipitation.
To modify supercooled clouds, meteorologists introduce substances that act as ice nuclei to trigger the formation of ice crystals. The following substances have been used for this purpose:
- Silver iodide: This is the most common agent currently used for seeding supercooled clouds. It is typically dispersed as minute particles via aircraft, ground generators, or pyrotechnic devices.12
- Dry ice: Historically, this was the first substance found to be effective. It works by cooling the surrounding air to approximately −78° C, causing ice crystals to form spontaneously.1
- Lead iodide: In some historical experiments, such as those conducted in the Soviet Union, lead iodide was used as an ice-nucleating agent in projectiles fired into clouds.1
While other materials like sodium chloride or calcium chloride are used in cloud modification, they are typically employed for seeding "warm" clouds (above 0° C) to encourage droplet growth rather than for seeding supercooled clouds.1