Does cloud seeding grow rain?
By Mark Wilcox
May 1, 2012 --
Despite waning state budgets, a major cloud seeding project got a $2.4 million nod of approval in Wyoming’s 2012 legislation to stay funded through 2014.
The project started as a five-year test in 2005 after years of drought-like conditions across the state. The state funded $8.25 million in research at that time until 2010. In 2010, researchers said they didn’t have enough data yet to present clear results about whether cloud seeding truly affected the weather. They got another biennium of funding: $2.85 million. The total tally for the Wyoming cloud seeding research now stands at $13.5 million, and the research seems unlikely to draw to a close by 2014 based on past data collection.
Some argue it is a waste of time and taxpayer money. Even the loose wallet of the federal government has remained all but closed to cloud seeding research for many years. But to the researchers, it is more than hocus pocus, and they argue the data collected during Wyoming’s project will offer credibility to cloud seeding projects everywhere.
Whether Wyoming’s weather
Wyoming’s cloud seeding research measures snowpack in several mountain regions: the Sierra Madres in the south-central part of the state, the Medicine Bow mountain range and the Wind Rivers. Of particular importance are the data collected from the Sierra Madres and the Medicine Bow range because of one critical factor. The ranges are similar enough that if a storm builds up simultaneously over the two ranges, one can be seeded while the other isn’t and researchers can quantitatively measure the difference in snowfall between the two storms.
Cloud seeding researchers have long battled the inability to provide sound scientific numbers for something they just know works to some degree. This setup was the focus of the first couple years of research in Wyoming. They needed a randomized statistical experiment to produce numbers entities wanting to use cloud seeding technology crave. So Wyoming enlisted a third party: Colorado’s National Center for Atmospheric Research. NCAR came up with the plot-to-plot data from the two similar ranges on “double crossover conditions.” When an appropriate storm develops over the two mountain ranges with the right amount of wind, moisture levels and temperatures, “then you call a case,” said Barry Lawrence, project manager for the Wyoming Water Development Commission. From there, a remote tech flips the switch, which randomly seeds only one of the two ranges. The cloud seeding generators on the chosen range light up and spew silver iodide in an invisible plume of smoke into the storm as high as 3,000 feet for four hours, the length of a case. Silver iodide then acts as an ice nucleus for water droplets to condense around, wringing an estimated 15 percent more snow out of the clouds, while only affecting 1 percent of airborne water vapor.
Then, high-resolution gauges can accurately measure how much and where snow fell, giving a snapshot of the storm.
“It doesn’t sound very sexy, and it’s not really all that sexy, but there’s a lot of work in that,” said Daniel Breed of NCAR’s research applications program. This setup creates an important numerical model to study.
If the right conditions persist, another case can be called.
“The key here is that techs never divulge which mountain range is seeded, so it’s blind from that perspective,” Lawrence said. “The evaluators have no vested interest in whether it works or not.”
And with the third party and blind results, measurements mean more.
“We’ve got a real credible experiment going on,” Lawrence said. “We’ve got the right people in place.”
And since cloud seeding has been around since the 1940s, NCAR’s advanced technology can monitor the silver iodide plume in ways never imagined by cloud seeding pioneers. But despite advances and seven years of research behind him, Lawrence can’t provide concrete data, saying they want to reach statistically pure 95 percent confidence in results, something he said could be possible with between 50 and 60 cases over the next two years.
“The reason we need that is what we’re trying to detect is fairly small versus natural variability,” Breed said.
A single year varies from between 15 cases and 40, meaning research may not be complete by the new 2014 deadline.
“Statisticians get real nervous when you start talking numbers when it’s not at critical mass,” Lawrence said. “It’s building layers of evidence; building a complete picture.”
Idaho Power in Wyoming
While Lawrence voices confidence in his experimental build and says the findings look good so far, others have run with cloud seeding in the state. Of note is cloud seeding done to increase hydrologic power generation by Idaho Power Co.
While currently the company only has cloud seeding generators placed in Idaho, it has its sights set on the Wyoming Range and the Salt River Range, which would provide “fuel” in the form of water for the company’s American Falls dam 100 miles downstream. If all goes smoothly, the company could have three $25,000 generators in place for this winter. As for now, the company is gathering surface data from Afton to support the project while enlisting NCAR to tell them where the generators ought to be placed. Though the generators designed to feed the Salt River and Greys River would be new to Idaho Power, the concept of feeding their cheapest power generation source by encouraging Mother Nature to create additional runoff is not.
“Cloud seeding really is just nudging Mother Nature,” said Shaun Parkinson, water management senior engineer for Idaho Power. “Basically you’re just allowing water vapor that’s there to precipitate out.”
Already the company has two installations in Idaho that feed dams across the state. And though the company doubted going in, it now spends $1 million annually to seed just its Payette project. Going into research phase in 2003 when its program started, officials said they were probably already convinced it wouldn’t work.
“We actually proved to ourselves it did work in trying to prove it didn’t,” said Engineering Leader Jon Bowling. “We are really confident this is a good program.”
It’s so good, in fact, that Parkinson said while they don’t have all the tools in place to make firm quantifications, they probably add close to 200,000 acre-feet of water to river flows annually. That’s more than 54 billion gallons of water. Assuming that water’s not used up for irrigation or other purposes prior to reaching the dam, that’s enough to generate as much as 100,000 megawatt hours.
“When the snow falls, it benefits a lot of folks besides Idaho Power,” said Derek Blestrud, staff meteorologist.
Which brings up the question of whether cloud seeding affects the weather downwind, simply relocating snow that might have fallen elsewhere and creating airborne water rights issues.
But Blestrud said Idaho Power has considered the issue, knowing the potential to disrupt the whole system.
“We’re not just hot-shotting, cowboying up,” he said.
Parkinson said some research has evaluated downwind effects. He said the effects of cloud seeding are neutral or positive up to 150 kilometers downwind.
“The storm is able to replenish,” he said.
Back in Wyoming, the National Science Foundation has funded a piggyback program to study the efficacy of cloud seeding to increase snowpack for the past five years. Tacked onto the research conducted by Lawrence’s state-funded program, researcher Bart Geerts, a professor of atmospheric science at University of Wyoming, said is the first time in nearly 30 years the National Science Foundation hasn’t left research like this high and dry.
Geerts said while agricultural interests, hydropower interests and other parties with economic stakes in cloud seeding believe it works, the scientific community is less enthusiastic.
“The scientific community is pretty much uncertain,” Geerts said. For his own research, Geerts has only had maybe 10 cases to study over his five years of involvement, only six of which stood out.
“One thing I have learned is that good conditions for seeding are not all that common,” he said.
And as far as evidence gathered so far, the jury is out.
“It’s very difficult to see a strong signal,” he said, otherwise scientists would have known decades ago. “The signal seems immersed in natural variability. There’s no obvious increase in snowfall rate.”
But to Geerts, the answer doesn’t matter as much as the research.
“We’re happy if we can publish good data,” he said.
Wyoming Business Report staff writer Mark Wilcox lives in Jackson and is delighted with anything that makes more snow fall there.