Let it snow: Illinois researchers help create precipitation
Professor and students join cloud-seeding project in Idaho
This scientific phenomenon is more than a rebuttal to popular belief—it’s the basis for a research effort underway by Illinois and several other institutions this winter that runs contrary to another old mantra: You can’t control the weather. Bob Rauber, professor of atmospheric sciences at Illinois, and his students are learning more about how to make it snow.
The team is part of SNOWIE (Seeded and Natural Orographic Wintertime Clouds – the Idaho Experiment), a cloud seeding project in southwest Idaho that scientists hope will teach them more about how to put more snow on the ground. More snowfall in the mountains would translate into more water for hydropower, irrigation, and other consumption in dry areas of the country.
“We want to convert water droplets in the cloud to ice crystals before the cloud sweeps over the mountains,” said Rauber, who is helping oversee the project, including Illinois operations.
Funded through the National Science Foundation, SNOWIE is designed to expand knowledge about cloud seeding, a process by which silver iodide is released into the clouds, either from the air or via ground-based generators. The presence of silver iodide, scientists believe, helps start the process by which liquid water turns into snow.
In addition, weak updrafts in these clouds and narrow cloud droplet distributions limit the impacts of any ice processes to multiply.
The silver iodide, Rauber explained, is considered an effective ingredient to help turn that super-cooled water into snow. In the case of the SNOWIE Project, the silver iodide is being released by an aircraft funded through Boise-based Idaho Power Company (which is also paying for some instrumentation in the project), while another research aircraft from the University of Wyoming and special Doppler radars placed on a mountaintop are taking measurements to understand the impact of the silver iodide.
Illinois has provided a rawinsonde system, which is basically a sophisticated weather balloon system to measure pressure, temperature, moisture, and wind speed and direction. Graduate students from Illinois, assisted by undergraduate students, are launching the balloons to record data during the research. The project, which began this month, will continue through mid-March, and it has already detected unequivocal signatures of cloud seeding effects with its airborne and mountaintop radars.
The work is heavily dependent on weather.
“That’s the crazy thing about studying weather,” said Rauber. “It’s not at all like a laboratory.”
“Part of understanding seeding is understanding the natural process of the storm,” he said. “It’s important to go out in the (storm’s) evolution to take measurements when seeding is not occurring.”
He added: “Results from SNOWIE are expected to provide a new and important understanding of cold-season precipitation—both naturally and that augmented through cloud seeding—and will have an impact throughout the American West, a region that increasingly suffers from drought and water shortage.”
Cloud seeding has been studied since the 1950s, Rauber said, but for years the research equipment was not sophisticated enough, and results did not withstand scrutiny very well. Until recently, the federal government withdrew funding from cloud seeding research, but it was carried on by western states and private companies. Growing environmental concerns and water shortages renewed interest in cloud seeding in recent years.
It’s not a new topic for Rauber, however. Cloud seeding was the subject of his research as he earned his doctoral degree in the 1980s.
“Essentially, I’m doing my PhD all over again,” he said, with a laugh. “But I’m doing it with a heck of a lot better equipment. Hopefully I can prove I was right.”
Dave Evensen. National Science Foundation contributed to the report.
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