University of Wyoming's Jeff French
Delivers Insights into Snowfall and Water Resource Availability
April 12, 2017
Can cloud seeding -- dispersing particles into the air with the aim of
increasing precipitation -- increase snowfall?
This winter, a team of researchers funded by the National Science
Foundation (NSF) conducted a cloud-seeding project in southwestern Idaho
to try to answer that question.
King Air prepares for flight during a snowstorm in Boise.
Cloud seeding is a process by which silver iodide is released into the
clouds from a plane or by ground-based generators. The silver iodide
particles provide surfaces on which ice nuclei can form, leading to
"I was surprised at the characteristics of the clouds in Idaho," says
Jeff French, a University of Wyoming (UW) atmospheric scientist and
principal investigator of the project, called SNOWIE (Seeded and Natural
Orographic Wintertime Clouds - the Idaho Experiment). "The air was
surprisingly clean, and the clouds had very low concentrations of liquid
Those conditions affect which processes in clouds are important, how
many droplets there are, how big they are, and ultimately how much snow
falls, French says. This winter in Idaho, that was a lot.
UW researchers used the NSF-funded King Air research aircraft to conduct
the cloud-seeding project from January 7 to March 16.
The project also included scientists from the University of Colorado
Boulder, University of Illinois at Urbana-Champaign, Boise State
University, the National Center for Atmospheric Research (NCAR) and the
Center for Severe Weather Research.
"SNOWIE is an important step in improving our understanding of cloud
seeding and winter precipitation in general," says Nick Anderson,
program director in NSF's Division of Atmospheric and Geospace Sciences,
which funded the project. "These scientists have conducted a successful
field campaign and now have a lot of data to analyze."
The research was conducted in concert with the Boise-based Idaho Power
Company, which obtains much of its electrical power through hydropower
dams that rely on snowfall as a source of water.
Idaho Power funded the aircraft that released the silver iodide, while
the King Air plane obtained measurements to understand the silver
iodide's effect, French says. The field work took place in and around
the Payette Basin, located approximately 50 miles north of Boise. SNOWIE
is considered the most comprehensive winter cloud-seeding study to date.
Idaho Power is interested in putting more snow on the ground in the
mountains, which leads to more water in rivers and, ultimately, more
power generation capability throughout the year.
Due to water shortages and droughts in some states and countries around
the world, cloud seeding is seen as a potential way of increasing water
supplies for communities and of irrigating crops. Water resource
managers, hydropower companies and agricultural organizations typically
pay for the process.
During SNOWIE, French says that the King Air operated in 24 intensive
observation periods that each lasted from 4-8 hours. During those
periods, researchers collected measurements in both seeded and unseeded
clouds over a range of atmospheric conditions.
An NSF-supported Doppler on Wheels (DOW) fleet of radar dishes mounted
on the backs of trucks was also involved.
"SNOWIE was very well-timed, happening during the snowiest winter in
Idaho in decades," says scientist Josh Wurman, director of the Center
for Severe Weather Research, which manages the DOWs. "There was so much
snow at the mountain sites that the DOWs are now marooned there until
spring, when the huge snow drifts melt enough for them to be extracted."
During the last week of the experiment, French says, the team had to
cease cloud-seeding operations as a result of the heavy snow. Idaho
Power's policies require that cloud-seeding be suspended, due to
potential flooding concerns, when an area exceeds 140 percent of maximum
normal snowpack on the ground.
At the end of the field work, French was still surprised by the clean
air in Boise; he had expected local industry to generate pollutants. The
reason for the clean air, he says, may involve the way aerosols in
surface air mix at higher altitudes.
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. Which leads to questions,
he says, "about how connected air is at the cloud level to air at the
surface. I'm not sure. This took us all by surprise."
Results from SNOWIE are expected to provide a new and important
understanding of cold-season precipitation -- both natural precipitation
and that involving cloud seeding -- that's important for communities
throughout the American West, a region that increasingly suffers from
droughts and water shortages, French says.
Next up: SNOWIE researchers will conduct numerical modeling of winter
cloud and precipitation processes using a supercomputer called Cheyenne
at the NCAR-Wyoming Supercomputing Center. The models will simulate
clouds and snow precipitation created in natural storms and with cloud
seeding over the Payette Basin.