[Bruce] Boe is one of several scientists working on the five-year Wyoming Weather Modification Pilot Project, an $8.8 million research program funded by the state of Wyoming. The project’s scientists, along with state water managers, hope to find proof of whether the decades-old practice of seeding clouds — trying to squeeze more precipitation out of passing storms — actually works and that it’s a practical option for increasing the state’s water supply. Members of the world’s science community — cloud-seeing advocates and skeptics alike — are watching the project closely. “For a scientist doing research, this is it. As far as in terms of the research, it is the biggest in the United States by far,” Boe said…
The Wyoming project is in its fourth year, only the second winter in which cloud seeding in earnest has actually been performed. The first two years involved mostly taking measurements and weather readings, obtaining permits from the U.S. Forest Service, gathering other statistical data and getting equipment in place…
While Boe’s company is contracted to perform the cloud-seeding operations, independent teams of scientists from the Colorado-based National Center for Atmospheric Research and the Desert Research Institute in Nevada are independently evaluating whether any increases in precipitation that occur are from cloud seeding or from just normal variations in the weather. That’s the real trick to proving if it works. Cloud-seeding scientists estimate that, if done properly, pumping silver iodide into a cloud will increase snowfall in most cases by about 10 to 15 percent. That’s roughly the same percentage of natural variability possible in normal weather patterns…
It’s too early to say with any certainty that Wyoming’s cloud seeding is working to make more snow, but the scientists are beginning to amass a massive amount of vital information from the project. They still have much more data to collect. They conducted 26 four-hour seeding events in southern Wyoming last winter and more than 30 this winter. Ideally, they would like to have more than 200 cases to examine by the end of the five-year project…
While clouds are often seeded from airplanes, the seeding on the Wyoming project this winter is all being done from the ground by generators on 20-foot towers. Inside a generator placed upwind, a propane flame heats the silver iodide solution, and a nozzle sprays it into the air. It rises into the cloud and is carried by the wind to a target area, which is where the scientists want it to snow. There are eight generators in each mountain range, the Snowies and the Medicine Bows, and another seeding site on the west side of the Wind River Range that has 10 generators.
Meteorologists determine when conditions are right for seeding and tell the technicians which generators to turn on. The technicians, sitting many miles away at computers, activate the generators remotely through satellite modems. Boe, using a machine in his cabin called an acoustic ice nucleus counter, checks the outside air during seeding operations to detect the presence of silver iodide to make sure the particles are reaching the target area…
Before, during and after seeding events, the weather is monitored closely. Independent evaluation teams from NCAR and DRI check the snow for the presence of silver iodide and to collect other statistical data. Seed generators are never turned on at the same time in both the Snowy Range and Medicine Bow Mountains — only randomly either in one mountain range or the other. The forecasters and evaluators are not told which mountain range was seeded, which should eliminate any bias in their predictions and conclusions, said Dan Breed, lead scientist for NCAR. Seeding only one range at a time also allows researchers to collect a double dose of data from each storm — one from a seeded mountain range and one that only received natural snowfall. Comparing results between the two ranges could help determine if increases in snow were a result of seeding or that ever-elusive variability that occurs with natural snowfall…
Periodically this winter, [University of Wyoming] professor Bart Geerts and graduate students will fly over snowstorms in a Kingair research aircraft as cloud-seeding experiments are going on to study how the clouds are affected. Using technologies called cloud radar and LINAR, short for Light Detection and Ranging, the crew will take snapshots of the clouds similar to the three-dimensional slices of a medical MRI scan. “We are basically trying to look at it in the finest detail in time and space. We’re actually looking at the cloud as it is injected with silver iodide,” Geerts said. When a cloud is seeded, “The idea is that silver iodide injected into a cloud is going to turn all that liquid water into ice pretty quickly. We want to see if that really happens.”[…]
University of Tennessee professor Glen Tootle is leading a study on the effects of an increased snowpack on spring and summer runoff. The university experiment could determine what a small snowpack increase in the Medicine Bow Mountains would mean for the North Platte River drainage. No one knows for sure if 10 percent more snow created from cloud seeding would necessarily produce 10 percent more water for the state’s supply. “Those basic questions have not been answered,” Geerts said.
