Let it snow: Scientists take first cloud seeding measurements

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By Daniel Strain
Special to The SUN
For the first time, researchers have used radar and other tools to accurately measure the volume of snow produced through cloud seeding.
The research took place in western Idaho’s Payette Basin in January 2017 and was led by Katja Friedrich, an atmospheric scientist at the University of Colorado Boulder.
Cloud seeding, which mixes tiny particles into the air to generate snowfall, has become an increasingly popular tool in water-strapped states like Idaho and Colorado. It’s also notoriously difficult to measure.
But that’s just what Friedrich’s team did, monitoring three attempts at cloud seeding from start to finish. Collaborators on the project included researchers from the National Center for Atmospheric Research in Boulder, University of Wyoming and University of Illinois at Urbana-Champaign.
“We tracked the seeding plume from the time we put it into the cloud until it generated snow that actually fell onto the ground,” said Friedrich, an associate professor in the Department of Atmospheric and Oceanic Sciences.
In all, the three cloud seeding events produced a total of about 282 Olympic-sized swimming pools worth of water. The group reported its findings recently in the Proceedings of the National Academy of Sciences.
Friedrich added that the research is an important first step toward better understanding just how efficient cloud seeding can be at creating those winter wonderlands.
“Everyone you talk to will say even if you can generate a little bit more snow, that helps us in the long run,” she said.
In the new study, that little bit of additional snow kicked off with an airplane. The vehicle used a series of flares to inject particles of silver iodide into a natural cloud formation that was passing overhead.
The idea behind such cloud seeding is to turn lightweight water vapor into heavy droplets.
“If everything goes according to plan, the water droplets will begin to freeze around the aerosols, forming snow,” Friedrich said.
But, she added, it’s also tricky to get a good sense of just how effective that transition really is, which is why most cloud seeding statistics lead to inconclusive results. Estimates range anywhere from zero to 50 percent additional snowfall, Friedrich said.
She and her colleagues, however, had a plan: During those January flurries, they used a radar dish to peer into the clouds as the water inside thickened and eventually succumbed to gravity.
The first attempt at cloud seeding, for example, dusted roughly 900 square miles of land in about a 10th of a millimeter of snow.
“If we hadn’t seeded these clouds, they would not have produced any precipitation,” Friedrich said.
Some in Colorado have high hopes for that process, too.
In 2019, the state entered into a partnership with six others that border the Colorado River to step up its efforts at cloud seeding — an attempt to increase the supply of water to that valuable waterway.
Friedrich added that, for now, she can’t say how useful cloud seeding might be for such efforts moving forward — every winter storm is different and interacts with aerosols in different ways. But the group’s findings could get scientists closer to being able to make those cost-benefit calculations.
“We can now finally put a number on how much water we can produce through cloud seeding,” Friedrich said.