As drought looms, could this team of scientists prove cloud seeding works?

The Mod Squad.

THE RESEARCHERS HAD ALREADY DONE FOUR FLIGHTS, earlier in January, before they saw the first hints of what they were looking for. The crew of meteorologists, atmospheric scientists, and students had converged near Idaho’s Snake River Basin, a horseshoe-shaped depression between ranges of the Rocky Mountains that is 125 miles at its widest point. Most of the state’s famous spuds come from this arable land. Each day that the weather was right—clouds containing the perfect amount of super-cooled moisture at the ideal temperature and altitude— the team flew up into the fluff, dropped silver iodide, and watched to see if they were making more snow than there would’ve been if they’d stayed home and hung on to their silver.

It’s called cloud seeding. And people have been planting little chemical seeds into puffy white masses, hoping to change the weather, for some 70 years. But after all that time, no one knows for sure how well it actually works: when or even if the practice makes more snow fall, or how. That’s what the team behind SNOWIE—an acronym for Seeded and Natural Orographic Wintertime clouds: the Idaho Experiment—had come to find out.

“These questions have been around since it started,” says Bob Rauber, one of SNOWIE’s principal ­investigators and a professor of atmospheric science at the University of Illinois at Urbana-­Champaign. He has been studying the phenomenon since the ’70s. Today, even though scientists have a computer model that theoretically calculates for success, “we don’t know if it’s right because we haven’t been able to validate it,” he says.

The day of that fifth flight, January 19, 2017, principal investigator Jeff French, an assistant professor of atmospheric science at the University of Wyoming, sat inside a tiny King Air prop plane. The pilot flew to 14,000 feet, then back down a couple thousand. The air just above them was around 5 to 14 degrees Fahrenheit, optimal for the super-cooled liquids needed to make snow. The plane’s radar was humming, as were instruments that collected information on atmospheric pressure, temperature, water vapor, and wind. The measurements poured into a set of computer-processor racks packed into the four-seater, making it look like the inside of a sound booth.

French knew that about 1,000 feet above, a second aircraft was sowing flares of silver iodide, cylinders lined up like firework cartridges before a show starts. These either smoldered in place on the plane, leaving a trail of particles drifting down, or sprung from its wings and burned out as gravity pulled them down to Earth. But French couldn’t see the other plane. In fact, he couldn’t see much at all. That is the thing about flying inside a cloud. What he could see was a feed from the plane’s radar in real-time, showing the cloud’s structure above and below him, and he could watch the cloud particles’ sizes, shapes, and concentrations change.

Below him, unseen, the land rose jagged and treeless at its highest points, ­blanketed in white. When that frozen snowpack melts each spring, it flows into the basin below, providing Idaho residents not just with household water, but also with electricity from the hydroelectric dams that power much of the state.

The craft above French flew back and forth, leaving silver iodide and, if they were successful, snow drifting in zigzags over the mountains. His plane then cruised through those plumes, its instruments able to see what French himself couldn’t: They could detect spikes in reflectivity that meant ice crystals were blooming, watch them travel with the weather, and perhaps discern whether snow actually appeared where the silvery chemicals had fallen.

On the ground below, radars at two remote mountain sites scanned for the same measurements. Staffed by students who’d snowmobiled up the slopes, these ­instruments were the first to see a zigzag suggesting they were indeed making snow.

THERE IS SOMETHING SEDUCTIVE ABOVE THE IDEA OF CONTROLLING THE WEATHER. Nature has foisted precipitation on humans forever, forcing us to be wet, iced-over, snowed-in, hail-stung, flooded, parched—whatever, whenever. Synthetic weather modification is the ultimate statement that we are supreme beings and can make the world perform to our needs. Programs developed in the 20th century thus try to mitigate hail, make it rain, curb hurricanes, and increase snowfall.

SNOWIE deals with only the latter. By necessity, the team’s attempt involved mountains, which play a role in creating and steering precipitation. When air approaches a mountain, it rises with the land itself. (After all, it can’t blow through rock and dirt.) This air chills as it ascends, and then condenses into an “orographic” cloud.

Inside clouds, natural snowflake embryos often form when ice crystals grow on tiny particles, like dust or gas or pollution. Scientists call these nuclei. To make more snow, the thinking goes, add more nuclei. Silver-iodide sprinkles have become the go-to material because when they bump into super-cooled liquid water, they reliably make it freeze if the temperature is below 21 degrees Fahrenheit. Ski resorts and drought-dry regions spend millions sending silver into the sky, but there’s ­actually no scientific consensus about whether the strategy works.

In 2015, the Cooperative Institute for Research in Environmental Sciences—a collaboration between the National Oceanic and Atmospheric Administration and the University of Colorado at Boulder—came the closest to a conclusion after evaluating a decade of snow-focused programs and research in a 148-page review. “It is reasonable to conclude that artificial enhancement of winter snowpack over mountain barriers is possible,” it stated. But later in the same paragraph the authors equivocated, saying: “No rigorous scientific study…has demonstrated that seeding winter orographic clouds increases snowfall. As such, the ‘proof’ the scientific community has been seeking for many decades is still not in hand.”

far-out plans for taming our weather
This way for other other far-out plans for taming our weather. Stuart Patience

THE IDEA FOR CLOUD SEEDING SOLIDIFIED—WHERE ELSE?—IN A FREEZER. Specifically, the freezer of General Electric scientist Vincent Schaefer. Schaefer had become interested in ice early, according to his 1993 obituary in The New York Times. When he was an ice-skating teenager, he obsessed over the structure of snowflakes and devised a way to transfer their likenesses to film before they disappeared. As an adult in the 1940s, he put some dry ice into a freezer and breathed into the cold box. “­Instantly the little cloud turned into tiny ice ­crystals,” the obit reports. Schaefer took that knowledge to the skies of Massachusetts in 1946 and dropped 6 pounds of dry ice from a plane. He watched water ice form and snow fall below the plane. That same year, physicist Bernard Vonnegut—writer Kurt’s brother—realized that silver iodide could also be used to seed clouds. Dry ice had to be dropped inside the cloud to work, but silver iodide could be sowed outside the cloud and drift in. Scientists have primarily used the compound ever since.

SNOWIE investigator Rauber worked on some of the big follow-on research projects that came after Schaefer and Vonnegut’s efforts. In Steamboat Springs, Colorado, he and his Ph.D. adviser, Lew Grant, impregnated clouds in an attempt to understand their inner churnings. It was basically like SNOWIE, he says, “but with instrumentation that was the ’70s and ’80s version of what we have today. We were walking around with Coke-bottle glasses.”

Other scientists conducted research as well, in states like Colorado, Montana, and Utah. One of the most conclusive experiments, in Australia in the aughts, suggested that seeding could increase snow by 14 percent. But even those results weren’t definitive. The equipment just wasn’t good enough to see what investigators needed to see.

Before SNOWIE, the last big study was 2005’s state-funded Wyoming Weather Modification Pilot ­Program. After nine years and $13 million, the final ­results weren’t conclusive. While one experiment showed no ­result from seeding, others suggested a possible ­precipitation uptick of 5 to 15 percent.

In 2014, Rauber and French, along with Bart Geerts, a professor of atmospheric science at the University of Wyoming, and Katja Friedrich, an associate professor of atmospheric science from the University of Colorado at ­Boulder, joined forces with the Idaho Power Company and the National Center for Atmospheric Research and approached the National Science Foundation. Collectively they possessed the brains and the brawn to answer all the lingering questions about cloud seeding, they said. And finally, they had the right glasses: instruments that were powerful enough to see it in action. SNOWIE’s radars can measure clouds with fewer and/or smaller particles; they can distinguish at much higher resolution spatially and temporally; they can use higher frequencies that are sensitive to smaller particles. In general, says French, they have a “significantly improved ability to directly measure cloud particles.” They would collect the same kinds of data they always had, but this time they could see the microphysics of the situation.

Idaho Power, which has run a seeding program since 2003 despite the scientific uncertainty, would use its plane to disperse the silver iodide and would run its ­usual data-collection systems. The scientists would employ instrument-laden planes and mountaintop radar stations. The information would be recorded on machines provided by the researchers, the National Center for Atmospheric Research, and Idaho Power, and would be pooled later for all of them to analyze. Together, they would evaluate what actually went on inside clouds, and what it meant for thirsty areas, ski resorts, and hydroelectric plants.

By now, these questions have taken on greater urgency. What may have ­started ­almost a century ago as a willful urge to make the weather more convenient for ­humans has evolved into a necessity to support drought-parched regions. The county of Los Angeles has funded seeding projects in areas that drain into its watersheds. Utah, California, and Idaho try to boost the snowpack that melts and then supplies their drinking water and drives their hydroelectric dams. Colorado ski resorts in Vail, Aspen, and Winter Park want more snow to survive their critical tourism season. “We’re very, very desperate for water,” says Friedrich, one of SNOWIE’s principal investigators. “That’s the bottom line. Even if it’s just a little bit of water, that helps.”

The second time the SNOWIE team submitted a proposal, the National Science Foundation agreed to sponsor the project.

THE GROUP SET UP ITS BASE IN IDAHO FROM JANUARY 7 TO MARCH 17, with the resources to do around 20 seeding sessions. Every day they would determine, via their own ­weather balloons and outside forecasts, whether the clouds saturated with super-cooled ­water would form at the right temperature and height over the mountains.

Josh Aikins, Friedrich’s graduate student, was a key member of the mountain radar group. He’d snowmobiled only once before, when he was a teenager on vacation in Vermont. But he quickly got the hang of sliding up to the Packer John Mountain radar site, at 7,000 feet of elevation—even when the snow was so new and light that the machine meant to float atop it instead sank down and needed to be dug out.

Aikins had fallen in love with snow as a kid when the Blizzard of ’96 blanketed the Mid-Atlantic. The snow drifted into banks that reached over the roof of his family’s York, Pennsylvania, home. He graduated from Penn State with a degree in meteorology but knew he didn’t want to be a weatherman. “I’m a T-shirt and shorts guy,” he says.

When the SNOWIE team decided to try for a seeding run, Aikins and the other radar-runners packed up a week’s worth of food and clothes into the vehicles; ­given that they were purposefully driving up the mountain during storms, they never knew how soon they’d be able to get back down. One time the 10-mile ride was so challenging, it required seven professional snowmobilers to help them out.

Each time they arrived at their site—a mountaintop with a radar system atop a big truck and an old camper as their luxury accommodations—Aikins would fire up the generator, warming up the radar and the camper. “We had a bunch of computers that we didn’t want to start up cold,” he says, because some electronic components won’t function well in that condition. They’d stash their clothes and food in the camper and dig out the drift-covered porta-potties.

Then they would scan with the radar and watch what the weather was doing. When the seeding started, they’d search for changes in reflectivity that suggested the electromagnetic waves were bouncing off an area of newly formed ice particles.

Aikins remembers well the day of the first signal. “We saw these linear bands coming through the area,” he says, referring to the radar readout. “It didn’t look natural.” He sent an email to the command center, asking if the planes were out. They were. “We could see the seeding in real time. We could see the path of the flares.”

In his public field report of that flight, principal investigator Geerts wrote ­impassively of their finding: “Possible seeding signature…two bands of higher reflectivity aligned with the seeding aircraft, drifting with the wind and dispersing over time.”

Put simply: They got it.

AIKIS AND GEERTS SOUND PRETTY STOIC ABOUT THAT FIRST FINDING, considering it was exactly the gold they’d gone West seeking. But that’s probably because, as Friedrich says, everyone was —and still is—suspicious. They haven’t fully analyzed the data. Their results haven’t undergone peer review and been published in an academic journal.

But their online reports note three instances where snow formation could be linked to their activity. The second time, Rauber wrote, “The seeding signatures were unmistakable and distinct, with the lines mimicking the seeder flight track.” They started to believe maybe the signatures weren’t a coincidence—and they wanted more. Soon enough, they were rewarded.

“The remarkable thing was not that we saw it,” says Friedrich, “but that we were able to repeat it multiple times.”

Rauber, who’s worked in seeding without certain results for decades, cops to his excitement. “Honestly, the first time we saw this, I was giddy,” he says. “I was almost dancing around in the room.” Think of it from “the perspective of an old cloud seeder,” he implores. He labored throughout the ’70s and ’80s, trying to see a signal those Coke-bottle glasses just couldn’t bring into focus. And now it’s like he’d had Lasik surgery.

Of SNOWIE’s data, Derek Blestrud—a meteorologist with Idaho Power and president of the North American Weather Modification Council—said, “What we got was well above and beyond what anybody imagined.”

Even though the team captured those zigzags, they still have a lot of work to do before they can tell the world exactly how—and how well—cloud seeding might work. Depending on who you ask, they’ll be ­digging into data for four to six years, although they aim to get the ­whiz-bang results out within 12 months. “We have more data than any of us ever dreamed of being able to collect,” French says.

The plane alone scooped up 25 gigabytes of data on each of its 18 flights, gleaned from the radar and laser systems, as well as from its direct temperature, pressure, and water-vapor probes. The scientists will sort through that and ground-based research, and do some interpretation and analysis on local machines at their universities and at the Center for Severe Weather Research in Boulder, Colorado. That will give them a rudimentary understanding of what the gigabytes signify: the physics of how snow forms and falls naturally in the mountains, how burning bits of inorganics alter them, the impact on weather as a whole. As French puts it, they’ll have 100 pieces of a 5,000-piece jigsaw puzzle.

To get the complete picture, they’re gonna need a bigger box—a supercomputer. The National Center for Atmospheric Research has a new one named Cheyenne, with 5.34 petaflops of capacity. It’s the 20th-fastest calculator on the planet. Cheyenne will show how well the physical observations—from the planes, the radars, and the real world—match up with the predictions. And based on how well they do or don’t, the SNOWIE team and other scientists can then tweak the predictors to better see which weather is the most fertile for modification.

This isn’t just about Idaho. SNOWIE will figure out the underlying mechanisms that determine how clouds come to form, evolve, and drop snow—whether seeded or not—down to Earth. “It should apply anywhere,” says Geerts. After all, physics is physics, on Earth as it is in heaven, as it is where the two meet.

Sarah Scoles is the author of Making Contact: Jill Tarter and the Search for Extraterrestrial Intelligence, published in July by Pegasus.

This story was originally published in the Extreme Weather issue of Popular Science.