March 13, 2006 1:21 PM PST
Cloud seeders say: Let it snow
A team of scientists and the state of Wyoming are on an atmospheric research mission to find out.
Since the 1960s, scientists, local water districts and ski resorts have attempted to produce more snowfall during drought years by "seeding" clouds with special particles to form ice crystals and larger water drops. But to date, the results have been mixed or inconclusive in producing precipitation. In some circles, cloud seeding is even dismissed as financially foolish or an unnatural work.
Now the National Center for Atmospheric Research and the Wyoming Water Development Commission have embarked on a five-year, $9 million experiment and research project to determine just how--or how well--it works, thanks largely to modern technologies.
"The major thing that's happened since the '60s is the development of new tools to understand what the results are," Roelof Bruintjes, a scientist at the NCAR, said in an interview Monday. Bruintjes is working on the Wyoming project with a team of NCAR scientists.
NCAR began its pilot project last month with initial cloud measurements and environmental assessments in Wyoming's Medicine Bow, Sierra Madre and Wind River mountain ranges. It also ramped up research this week, including some cloud seeding. "This year, we're essentially doing the design of the whole five-year program," said Bruintjes.
Momentum has built for a modern-day research project because of technology that can deliver quantifiable results. In the air, scientists now have airborne surface radars, high-tech satellites and lasers at their disposal to capture data on weather changes. Scientists also use microwave radiometers on aircraft to measure cloud liquid. Those radiometers weren't available 40 years ago.
On the ground, added computational power and high-resolution, computerized weather models help scientists magnify finite changes in weather processes in a way not previously possible. The computerized weather models map the terrain and the weather systems moving over it in detail. Instruments at select sites track precipitation rates, common meteorological variables, background air quality and ecosystem characteristics.
With that, Bruintjes believes, previously unanswered questions can be resolved in the next two years. Cloud seeding "does make larger drops and ice crystals, but there's a big black box in the middle: Does it produce more water on the ground?"
Despite the absence of verifiable results in the field, cloud seeding is big business. Western states like Wyoming spend millions of dollars annually on weather modification to produce fresh water or snow, but they can't prove quantifiably whether it works.
The water district of Wyoming, which has suffered years of drought, estimates that even a 10 percent boost in snowfall in areas the project is targeting would deliver a bounty of between 130,000 and 260,000 acre-feet of water in added runoff each spring. It estimates the value of extra water at between $2.4 million and $4.9 million, excluding the value of more hydroelectric power, better water quality and a potential boost to tourism.
Still, questions about tampering with the natural cycles of weather plague experiments in cloud seeding. Beyond that, scientists argue that in some areas, populations are already affecting clouds unintentionally through pollution.
"If cloud seeding is shown to work, it may help counteract the effects of air pollution as well as ease those of natural drought cycles," NCAR project scientist Dan Breed said in a statement.
The project was inspired by a report written by the National Research Council in 2003 examining "critical issues" in weather modification research. In it, the NRC urged that there be a coordinated national research program to answer questions about basic atmospheric processes with the help of new technology and the cost effectiveness of weather modification.
"The field of atmospheric science is now in a position to mount a concerted and sustained effort to delineate the scope and expectations of the future of weather modification research," according to the report, which is the first from NRC on the subject in 40 years.
Next year, the team will perform widespread cloud seeding in Wyoming's snow mountains.
Beginning next winter, pending permits, the project will start up 24 ground-based generators to burn a silver iodide and acetone solution that will release plumes of silver iodide particles into targeted clouds. At the same time, it will send a Piper Cheyenne II twin-engine turboprop airplane to burn flares mounted on its wings that will inject silver iodide into clouds 2,000 feet or higher above the ground.
The icelike particles of silver iodide attract the cloud's liquid water, which then freezes around the particles to form snow.
NCAR is working with others on the project, including researchers from the University of Wyoming, the South Dakota School of Mines and Technology, the Desert Research Institute and the U.S. Forest Service. The project also contracted Weather Modification, a private company in Fargo, N.D., to seed snow clouds. That company's aircraft will also be used for the research.
Bruintjes said weather has a natural variability that can interfere with the finding of exact results in research like this. Consequently, NCAR will also be doing some randomization, or experiments in target areas, to minimize that variability. With the experiments, they are trying to understand the physics of cloud seeding and how much more precipitation it causes under what specific conditions.
"These are the things we could not test 20 or 30 years ago," he said.
4 commentsJoin the conversation! Add your comment