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UW Wraps Up Cloud-Seeding Project in Southwestern Idaho

April 12, 2017
The UW King Air research aircraft is prepared prior to a flight in a snowstorm in Boise, Idaho.
The UW King Air research aircraft is prepared prior to a flight in a snowstorm in Boise, Idaho. UW led the SNOWIE Project -- cloud-seeding research funded through the National Science Foundation -- in southwestern Idaho Jan. 7-March 16. (Jeff French Photo)

Jeff French learned very quickly that clouds over Boise, Idaho, are much different from those he had previously observed over the Snowy Range.

“I was surprised at the characteristics of the clouds in Idaho,” says French, a University of Wyoming assistant professor in the Department of Atmospheric Science and principal investigator for the recent SNOWIE Project. “The air was surprisingly cleaner over there, and the clouds had very low concentrations of liquid drops.

“If you have the same amount of mass of liquid, but you have fewer droplets, this means the droplets have to be larger,” he adds. “That impacts what processes in clouds may be important; how many droplets you have; and how big they are.”

UW, with the use of its King Air research aircraft, headed a cloud-seeding project -- funded through the National Science Foundation (NSF) -- in southwestern Idaho Jan. 7-March 16. Cloud seeding is a process by which silver iodide is released into the clouds, either from the air or via ground-based generators. In the case of the SNOWIE Project, the silver iodide was released by a second aircraft funded through Boise-based Idaho Power Co. while the UW King Air took measurements to understand the impact of the silver iodide, French says.

The research, dubbed SNOWIE (Seeded and Natural Orographic Wintertime Clouds -- the Idaho Experiment), was conducted in concert with Idaho Power, which provides a good share of its electrical power through hydroelectric dams. The research took place within and near the Payette Basin, located approximately 50 miles north of Boise. It is considered, to date, the most comprehensive cloud-seeding study in winter.

Idaho Power is interested in putting more snow on the ground in the mountains, which leads to more water in the rivers and, ultimately, more power generation capability throughout the year. Due to water shortages and droughts in some states and in countries around the world, cloud seeding is seen as a potential way to increase water supplies for communities and to irrigate crops. Cloud seeding is typically paid for by water resource managers, power companies (hydropower) and agricultural interests.

“I think Idaho Power was really pleased. It was a wonderful working relationship,” French says. “It was a perfect example of a for-profit company -- that has its own agenda and needs and stakeholders -- working with publicly funded organizations on a project that neither group was otherwise able to do by itself.”

During the project, French says the King Air was able to operate in 24 IOPs (intensive observation periods) that lasted 4-8 hours each. During those IOPs, researchers collected measurements in both seeded and unseeded clouds over a range of atmospheric conditions.

“The last week of the experiment, we had to suspend cloud-seeding operations because so much snow had fallen in the basin,” French says, referencing Idaho Power policy that requires cloud seeding be suspended, due to potential flooding concerns, when the basin exceeds 140 percent of maximum normal snowpack on the ground.

Still, French remained a bit perplexed that the air was cleaner in Boise because he expected industry there to put more pollutants in the air compared to clouds in the Snowy Range, where there is no nearby industry. He surmised the reason may be how well aerosols within surface air mix to higher altitudes.

“If there is no way for aerosols to get up to 14,000 feet, that air at 14,000 feet would be very clean,” French says. “How connected is the air at the cloud level to air at the surface? I’m not sure why. It took us all by surprise.”

Spencer Faber, a UW master’s degree student from Guernsey majoring in atmospheric science, worked the bulk of the project as an instrument operator aboard King Air.

“I was responsible for monitoring a variety of instruments -- including cloud water content probes, a cloud droplet counter, cloud particle imagers and a LiDAR -- and troubleshooting issues should they arise,” he explains. “I also kept an eye on incoming data that were important both for the scientific mission and crew safety. We really had to watch out for icing.”

Faber, who will graduate in May and previously earned his bachelor’s degree in earth systems science from UW, says the experience improved his skills as a researcher and scientist.

“Flying on the King Air and seeing all the data in real time gave me a completely different perspective on cloud processes and the highly dynamic nature of cloud systems,” he says. “I have lots of experience analyzing aircraft data, but seeing everything firsthand really helped me put together the big picture.

“SNOWIE also was valuable because it gave me a glimpse into just how difficult it can be to run a successful field campaign,” he adds. “The team had a lot to deal with between the highly variable schedule -- 3 a.m. mission briefings, making accurate weather forecasts, coordinating with seeding aircraft and DOWs (Doppler on Wheels) -- and tackling some pretty perplexing instrument issues.”

Adam Tripp, from Idaho Springs, Colo., and Adam Majewski, from Pittsburgh, Pa., both UW Ph.D. students, also assisted French. The cloud-seeding project included researchers from the University of Colorado, University of Illinois-Urbana/Champaign, Boise State University and the National Center for Atmospheric Research (NCAR’s) Research Applications Laboratory.

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, French says.

“SNOWIE field research was an important step toward improving our understanding of cloud seeding and winter precipitation in general,” says Nick Anderson, program director in the NSF’s Division of Atmospheric and Geospace Sciences, which funded SNOWIE. “From an early look at the data, the scientists have conducted a successful campaign and have a lot of important data to analyze.”

Numerical modeling of cloud and precipitation processes will be conducted using the supercomputer, nicknamed Cheyenne, at the NCAR-Wyoming Supercomputing Center. The numerical models will simulate clouds and snow precipitation -- created in natural storms and with cloud seeding -- over the Payette Basin.

“I think we have enough information to do computer modeling on these storms for the next two and a half years,” French says.

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