Here’s the release from NCAR/UCAR (David Hokansky):
Scientists announced today that they have successfully used a combination of radars and snow gauges to measure the impact of cloud seeding on snowfall. The new research addresses decades of speculation about the effectiveness of artificial methods to increase precipitation, demonstrating unambiguously that cloud seeding can boost snowfall across a wide area if the atmospheric conditions are favorable.
“This is a revelation,” said Sarah Tessendorf, a scientist at the National Center for Atmospheric Research (NCAR) and co-author of a new paper about the research. “We can definitely say that cloud seeding enhances snowfall under the right conditions.”
The researchers, including scientists from the University of Colorado Boulder, University of Wyoming, and University of Illinois at Urbana-Champaign, arrived at their results by analyzing detailed observations taken in a cloud seeding experiment in Idaho during the winter of 2017. They found that injecting clouds with silver iodide generated precipitation at multiple sites at the ground, sometimes creating snowfall where none had existed.
The study provides the most comprehensive evidence to date that cloud seeding can generate rain or snow.
Tessendorf cautioned, however, that successfully producing precipitation requires the presence of clouds. The results are also dependent on such atmospheric factors as local winds. Even when cloud seeding enhances precipitation, there are additional factors that will determine if it is a cost-effective approach to increasing snowpack or replenishing reservoirs.
“The seeding produces ice and that ice can form snow, but is it enough additional snow to make it cost effective?” she asked. “For water managers, the bottom line is the amount of snowpack that you’re building over the whole winter and how much runoff it will generate. We are looking into some promising approaches to address those bigger questions, but we still have plenty of work to do to get there.”
The study was published this week in Proceedings of the National Academy of Sciences. Funding came from the National Science Foundation (NSF), which is NCAR’s sponsor, and from the Idaho Power Company.
A scientific challenge
As far back as the 1940s, scientists demonstrated that injecting certain types of particles into clouds could induce ice to form and grow around them until they fell out of the clouds.
But measuring what effect, if any, cloud seeding had on measurable rain or snow proved very difficult. Researchers compared the amount of precipitation from randomly seeded clouds with similar clouds that were not seeded, but such statistical analysis produced mixed results, partly because natural precipitation is so variable that it is difficult to pick out the signal from the noise. Other work has indicated that cloud seeding can boost precipitation at specific locations, but left open the question of whether the increase in precipitation extended across significant areas.
To tackle the question, NSF and the Idaho Power Company launched a major field project in the winter of 2017 called SNOWIE (Seeded and Natural Orographic Wintertime clouds — the Idaho Experiment). Researchers used airborne and ground-based radars, high-resolution snow gauges, and computer modeling to quantify the impact of injecting silver iodide into clouds over the Payette Basin region north of Boise. The seeding aircraft released silver iodide along a flight path that resulted in a zigzag pattern of seeding effects in the clouds.
This approach enabled the research team to observe the entire process and compare the side-by-side seeded and unseeded areas.
“We tracked the seeding plume from the time we put it into the cloud until it generated snow that actually fell onto the ground,” said Katja Friedrich, a professor at the University of Colorado Boulder and lead author of the new study.
The results show that, on at least three occasions, the seeding measurably boosted the snowfall across the targeted watershed. A cloud seeding flight on January 19, 2017, for example, generated snow for about 67 minutes, dusting roughly 900 square miles of land with about a tenth of a millimeter of snow above the minimal amount that was falling naturally.
The three cases highlighted in the study produced a combined total of 571 acre feet of water, or the equivalent content of about 285 Olympic-sized swimming pools.
Other cloud seeding attempts, however, were not so easily detected and may not have been successful. Tessendorf said the research team is continuing to analyze 18 additional attempts during SNOWIE in order to learn under what conditions the seeding effect can be detected and result in an increase in precipitation.
he results from SNOWIE can be used to improve computer models of cloud seeding processes and better inform officials as they make decisions about their particular priorities, Tessendorf said. Ski resorts might want to increase snow on selected days, whereas water managers would want to build up snowpack over the course of the winter in order to generate additional spring runoff.
“We’re going to need to dig deeper into the data and further quantify the seeding impact,” Tessendorf said. “It’s important to find out whether this enhances snowpack in a way that meets specific needs. ”
About the article
Title: Quantifying snowfall from orographic cloud seeding
Authors: Katja Friedrich, Kyoko Ikeda, Sarah A. Tessendorf, Jeffrey R. French, Robert M. Rauber, Bart Geerts, Lulin Xue, Roy M. Rasmussen, Derek R. Blestrud, Melvin L. Kunkel, Nicholas Dawson, and Shaun Parkinson.
Publication: Proceedings of the National Academy of Sciences
From Colorado Public Radio (Grace Hood):
The end result was a critical research finding: On three occasions, injecting clouds with silver iodide generated significant precipitation, more than doubling the rate of snowfall that had been falling naturally…
Cloud seeding is the deliberate injection of substances like silver iodide by airplane to create precipitation. The practice dates back to the 1940s when American chemist Vincent Schaefer used airplanes — and even cannons — to inject clouds with silver iodide or dry ice. While the industry around cloud seeding has existed for decades in the United States, the ability of science to verify results has been more ambiguous.
Scientists flew an airplane that had high-resolution cloud radar that could see features in clouds that are undetectable to the naked eye. Scientists also positioned mobile Doppler radars on wheels that storm chasers use high in the mountains above basins to observe changes in weather.
“Having these mobile radars positioned up on top of mountain ridges to be able to see over the basins where we were targeting cloud seeding, we were able to get measurements that we wouldn’t have seen otherwise,” [Sarah] Tessendorf said.
From KUNC (Luke Runyon):
A lot of the current water scarcity problems in the Southwest could be eased if it just snowed more and with a regular frequency in the high country of Colorado, Utah and Wyoming. More snow means more time to deal with the Colorado River’s fundamental supply and demand imbalance.
The onus to correcting that imbalance often falls more on the demand side of the equation, with myriad policy pushes that either incentivize or force people to use less water. On the supply side, options are limited.
There’s one tempting proposition for western water managers currently feeling the pressure to dole out cutbacks to users due to the region’s ongoing aridification — inducing clouds to drop more snow.
For decades, states have invested in weather modification programs, also known as cloud seeding, in the hopes of boosting precious snowpack. The practice showed up in a recent agreement among Colorado River Basin states, and investment is expanding, with water agencies in Wyoming and Colorado for the first time putting funds toward aerial cloud seeding, rather than solely relying on ground-based generators.
“I can say that we’re up significantly in the last 24 months on the number of smaller large-scale programs that we’re modeling and completing feasibility studies for,” says Neil Brackin, CEO of Weather Modification, Inc., a North Dakota-based cloud seeding company that operates across the Western U.S.
Brackin’s company is in charge of the Colorado and Wyoming aerial programs, flying cloud seeding operations when moisture-laden snow storms arrive in northern Colorado’s Never Summer range or southern Wyoming’s Medicine Bow and Sierra Madre ranges…
It’s not snowing when we visit the generator, but Hjermstad agrees to fire it up to demonstrate how it works. First, he gets propane flowing and then turns on a valve to the silver solution. With a fire starter, he lights the chimney on top. A bright orange flame flares from the generator, sending microscopic bits of silver iodide into the air.
If there was a storm right now and the wind was blowing the right direction, Hjermstad says, this generator could be influencing how much snow it eventually drops…
There is a certain class of clouds that are ripe for seeding, he says. Some clouds arrive in Colorado full of supercooled liquid water, but they’re not dropping that moisture. By injecting small particles into the cloud, a snowflake is able to form. The silver iodide acts as the “seed,” which enables the growth of a new ice crystal. That new snowflake can ricochet through the cloud, amplifying its impact…
From late November to April, Hjermstad keeps an eye on each weather system forecast to drop snow or pass over his generators. If it looks promising, he’ll contact the landowners where the generator sits, tell them when to turn it on and turn it off, and watch its track on radar with ground truthing courtesy of Colorado’s highway webcams.
For decades, the practice has had a problem with its reputation. Anecdotal accounts from farmers and ski resort owners confirmed cloud seeding effectiveness. Recent scientific studies have given it more credence, but top experts in the field argue there’s still a lot we don’t know about how well cloud seeding works…
Parked in a hangar outside Laramie, Wyo., we’re sitting inside the small research plane French uses to study clouds. To get to know a cloud, he says, you can’t just look at it from the outside, you need to get inside it. An expensive suite of on board instruments lets him look at how snow forms in real time.
“Ice crystals come in many many different shapes,” French says. “They can look like six-sided plates. They can look like long needles or columns. They can look like dendrites, which is kind of the typical snowflake shape.”
For years, French has devoted much of his research to understanding the science behind cloud seeding. In 2017 he partnered with the Idaho Power Company and other researchers to fly the research plane behind another plane that was seeding clouds. The result was a series of scientific articles. A 2018 report French co-authored showed for the first time how aerial cloud seeding worked…
The study, called “Seeded and Natural Orographic Wintertime Clouds: The Idaho Experiment” (SNOWIE) and conducted in the Payette River basin near Boise, Idaho, was a big deal. Before then, no one had solid evidence that showed the physics of cloud seeding working in the real world.
With new data in hand, French was able to say, “Yes, the amount of snow that was falling at this location increased.”
That might sound like a definitive endorsement of cloud seeding effectiveness. But the scientists producing the research are circumspect about their findings, and ready to caution people from taking away too much from SNOWIE’s early results…
Sarah Tessendorf is a researcher at the National Center for Atmospheric Research in Boulder, Colo. and worked with French on SNOWIE. People ask her frequently if cloud seeding works. And she says it depends on how you define “work.” If the question is whether or not cloud seeding is capable of producing more ice inside a cloud, then the answer is yes. But more often than not, the question is more complicated and people are hoping for more than that.
“So, sometimes the question … is, ‘Does it produce additional snowpack on the ground?’ And we’re still working to try to answer that question,” Tessendorf says.
Tessendorf is cautious about what she’s currently able to prove when it comes to cloud seeding. In the past, studies have shown the practice could boost snowpack by up to 15 percent. Tessendorf says the increase in snowpack cited in those studies has been a moving target over the years, with varying levels of rigorous data gathering. When she and other researchers want solid proof, they’re looking for a 95 percent level of confidence that cloud seeding caused the increase, and it wasn’t just a serendipitous series of storms…
In a gilded Las Vegas conference room in December 2017, water managers detailed their solutions to the Colorado River basin’s chronic water scarcity, and how to wean the Southwest from total reliance on the overtaxed river.
A representative from the Upper Colorado River Commission laid out what Colorado, Wyoming, New Mexico and Utah would bring to the table. A three-pronged Drought Contingency Plan included a focus on demand management, which would create a dedicated pool of saved water within Lake Powell. Another prong dealt with reservoir operations to streamline decision making between state and federal agencies. The third was a re-commitment to weather modification programs which had been in place in some form since 2007.
In mid-2018, before wrangling over Colorado River Drought Contingency Plans reached a fever pitch in the river’s Lower Basin, water agencies in California, Arizona and Nevada agreed to spend upwards of $1.5 million each year on cloud seeding programs in the watershed’s upper reaches.
“The reason that cloud seeding is being implemented on a relatively large scale in the Colorado River basin is it’s a very low-risk, high-reward scenario,” says Dave Kanzer, an engineer with the Colorado River District and manager of the Central Colorado Mountain River Basin Weather Modification Program, which receives funds from Lower Basin water agencies.
If you’re a water manager in the Southwest, it’s easy to think of cloud seeding like an extra battery for a smartphone. The guy selling the battery tells you it will probably only charge your phone another four or five percent, maybe more if you plug it in at exactly the right time. So it’s not reliable, but it’s the cheapest on the market. Every other battery is expensive and takes years to make. And if a lot of people are counting on you to make a call, you might just be willing to buy the battery, even if it ends up doing nothing in the end.
Kanzer says investors understand the risks involved with cloud seeding. They’re not under a delusion that it will be the basin’s saving grace…
Colby Pellegrino is with the Southern Nevada Water Authority, the water utility for Las Vegas, and says her agency’s investment in Upper Basin cloud seeding is worthwhile.
Here’s a release from the University of Wyoming:
Two University of Wyoming researchers contributed to a paper that demonstrated, for the first time, direct observation of cloud seeding using radar and gauges to quantify the snowfall. Traditionally, cloud seeding — used to increase winter snowpack — has been evaluated using precipitation gauges and target/control statistics that led mostly to inconclusive results.
The research, dubbed SNOWIE (Seeded and Natural Orographic Wintertime Clouds — the Idaho Experiment), took place Jan. 7-March 17, 2017, within and near the Payette Basin, located approximately 50 miles north of Boise, Idaho. The research was in concert with Boise-based Idaho Power Co., which provides a good share of its electrical power through hydroelectric dams.
“This looks at how much snow falls out of seeded clouds at certain locations. That’s what’s in this paper,” says Jeff French, an assistant professor in UW’s Department of Atmospheric Science and fourth author of the paper. “We want to see if we can apply what we learned over a number of cases over an entire winter.”
The paper, titled “Quantifying Snowfall from Orographic Cloud Seeding,” appears in the Feb. 24 (today’s) issue of the Proceedings of the National Academy of Sciences (PNAS), one of the world’s most prestigious multidisciplinary scientific journals, with coverage spanning the biological, physical and social sciences.
The paper is a follow-up to a previous PNAS paper, by the same research team, titled “Precipitation Formation from Orographic Cloud Seeding,” which was published in January 2018. That paper focused on what happens in the clouds when silver iodide is released into the clouds. In the case of the SNOWIE Project, the silver iodide was released by a second aircraft funded through Idaho Power Co., while the UW King Air took measurements to understand the impact of the silver iodide, French says.
Katja Friedrich, an associate professor and associate chair of atmospheric and oceanic sciences at the University of Colorado-Boulder, was the newest paper’s lead author. Bart Geerts, a UW professor and department head of atmospheric science, was sixth author on the paper. Other contributors were from the University of Illinois at Urbana-Champaign, the National Center for Atmospheric Research (NCAR) and Idaho Power Co.
Throughout the western U.S. and other semiarid mountainous regions across the globe, water supplies are fed primarily through snowpack melt. Growing populations place higher demand on water, while warmer winters and earlier spring reduce water supplies. Water managers see cloud seeding as a potential way to increase winter snowfall.
“We tracked the seeding plumes from the time we put the silver iodide into the cloud until it generated snow that actually fell onto the ground,” Friedrich says.
French credits modern technology, citing the use of ground-based radar, radar on UW’s King Air research aircraft and multiple passes over a target mountain range near Boise, with making the detailed cloud-seeding observations happen. Despite numerous experiments spanning several decades, no direct, unambiguous observation of this process existed prior to SNOWIE, he says.
Over the years, research of cloud seeding “has been clouded,” so to speak, Geerts adds. He says it was difficult to separate natural snowfall and what amount was actually produced through cloud seeding. However, this study was able to provide quantifiable snowfall.
“Natural snowfall was negligible. That really allowed us to isolate snow added through cloud seeding,” Geerts says. “However, we are still in the dark where there is lots of natural snowfall.”
Following a brief airborne seeding period Jan. 19, 2017, snow fell from the seeded clouds for about 67 minutes, dusting roughly 900 square miles of land in about one-tenth of a millimeter of snow, based on the team’s calculations. In all, that cloud-seeding event and two more later that month produced a total of about 235 Olympic-sized swimming pools’ worth of water.
Other observations where snow from cloud seeding was measured took place Jan. 20 and Jan. 31 of that year.
In all, the UW King Air made 24 research flights or intense observation periods (IOPs) lasting 4-6 hours each during SNOWIE. Of those IOPs, cloud seeding occurred during 21 of the flights. During the last three flights, Idaho Power had to suspend cloud seeding because there was so much snow in the mountains already.
While a good deal of research took place aboard the King Air, much of it also occurred on the ground. Numerical modeling of precipitation measurements was conducted using the supercomputer, nicknamed Cheyenne, at the NCAR-Wyoming Supercomputing Center. The numerical models simulated clouds and snow precipitation — created in natural storms and with cloud seeding — over the Payette Basin near Boise. The numerical models also allow researchers to study future storm events where measurements have not been obtained in the field.
While the 24 cloud-seeding flights by King Air was a good start, Geerts says, in an ideal world, even more flights are necessary to learn more about cloud seeding in other regions of the country.
Friedrich adds that the research is an important first step toward better understanding just how efficient cloud seeding can be at creating those winter wonderlands.
“Everyone you talk to will say, even if you can generate a little bit more snow, that helps us in the long run,” she says.
French says the team has applied for a new National Science Foundation grant to continue analyzing cloud-seeding data collected from the remaining research flights during 2017.
“We will look at areas where natural snowfall occurs,” French says. “We’ll take what we learned and see if we can quantify how much snow was produced through silver iodide in areas already receiving snow.
“When we get done with the next three years, we’d like to go out and make similar-type measurements in Wyoming, Colorado or Utah, where clouds may have different characteristics,” French adds. “We can broaden the types of clouds we can sample.”
This video shows Drone footage from the top of Granite Peak in Idaho as we were digging out the Doppler On Wheels (DOW) mobile radar, RV trailer, and porta potties that were deployed for the Seeded and Natural Orographic Wintertime Clouds: The Idaho Experiment (SNOWIE) scientific field campaign. This site was called the “Snowbank” site during the project due to the roadway that leads to Snowbank Mountain just to the north of Granite Peak. I was the CU Boulder graduate student lead working with the Center for Severe Weather Research (CSWR) to operate the DOWs during SNOWIE.