Rainmakers: The Drones Used to Seed Clouds
On 23 August, Cooper Freeman had no idea that clouds above Homer, Alaska, were being seeded with silver iodide to encourage precipitation. Thousands of other residents were also unaware of the experiment, which was conducted by California-based start-up Rainmaker.
The company says its three-hour operation generated an estimated 19 million US gallons of additional precipitation over the Kenai Peninsula. Rainmaker experimented using drones equipped to release silver iodide into suitable clouds.
Cloud seeding is more than 80 years old and involves introducing materials such as silver iodide into clouds to encourage the formation of ice crystals. When those crystals grow large enough, they can fall as rain or snow, depending on atmospheric conditions.
The process does not create clouds or rainstorms from clear skies. Instead, it works with existing clouds under suitable conditions, particularly in cold or mountainous environments. Rainmaker’s own description of its technology confirms that precipitation cannot be generated without existing clouds.
Rainmaker founder and CEO Augustus Doricko said the company releases about 20 grams of silver iodide per flight across large areas. He said the resulting increase in ground-level concentration is measured in parts per quadrillion and is below the threshold he cited from the US Food and Drug Administration.
Freeman, Alaska director of the Center for Biological Diversity, has raised concerns about the lack of widespread public notification and the environmental impact of the material released during the experiment.
“It doesn’t appear that there was any downstream monitoring to verify that this silver iodide didn’t impact the environment,” Freeman said.
He also questioned whether cloud seeding can meaningfully address water shortages, saying the approach could distract from efforts to improve water conservation.
The reported 19 million gallons should also be viewed in context. Rainmaker’s figure is an estimate of additional precipitation rather than 19 million gallons collected at a single location. Alaska environmental officials have described the figure as a modeled estimate, equivalent to about 0.01 inch of precipitation across the area analyzed.
Interest in weather modification technology is growing as concerns over water security increase. More than 50 countries are developing or operating cloud-seeding programmes, while companies are exploring new ways to improve how precipitation is produced and measured.
For Rainmaker, the Alaska experiment was part of research into drone-based cloud seeding. The company says its operations are intended to improve targeting and validation of precipitation enhancement.
The experiment also leaves questions about environmental monitoring, public notification and the effectiveness of silver iodide cloud seeding. Those issues are likely to remain central as private companies expand their work in weather modification.
