The quest to change the weather

Extreme weather seems to be increasingly frequent. — (Image credit: Courtesy of Steffany Royal)

The storm is fierce and glowing turquoise, and Steffany Royal is waiting for it at the border of Montana and North Dakota, circling 7,000 feet high in a tiny Piper Seneca.

Back on the ground, Wayne Mrnak, a sixth-generation North Dakota farmer, fearfully watches the sky. The strange tropical-ocean-colored clouds indicate light reflecting off bits of ice in the storm's core. This means hail, a potential death sentence for farmers like Mrnak, whose 6,000 acres of wheat, barley, corn, and sunflowers lie striped across picturesque rolling plains in the state's southwestern corner, near the Badlands. "We've had hailstorms here where there is nothing left," says Mrnak. In mere minutes, millions of dollars of plant material can be smashed to bits. It's a crop's version of death by stoning.

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Florida has the sun, Buffalo gets snow, and the Gulf Coast faces hurricanes. North Dakota is hail country. In late spring and summer, winds blowing east over the Rocky Mountains tap moisture streaming north from the Gulf of Mexico to create massive thunderstorms on the Great Plains that frequently produce hail. Unfortunately, the hail belt also happens to be the farm belt. In North Dakota, about 90 percent of the land is covered by crops or used for cattle ranching, meaning if it is hailing, someone's plants are probably getting pelted, if not completely crushed.

Hail in this region can tear the shingles off roofs, pock cars so badly, they look as if they were sprayed from above with a machine gun, and pile so deep that snow plows need to be called out; a 1980 storm in Orient, Iowa, left hail drifts 6 feet high. Death comes with hail: The ice chunks bludgeon to death birds, cows, and people. The last known human fatality in the U.S. was in 2000, when a 19-year-old Texas man was struck by a softball-size hailstone estimated to be traveling at 100 miles per hour.

Royal's employer is Weather Modification Inc., or WMI, the world's largest company of its kind, and one of the oldest, started by a group of Bowman, N.D., wheat farmers in 1961. "To call what we do ‘weather modification' is misleading," says WMI Vice President of Meteorology Bruce Boe, a sturdy man with a crew cut and a master's degree in atmospheric science. "We are not modifying weather so much as modifying clouds."

The history of weather modification was, until fairly recently, littered with failures. In the 1st century, the Greek historian Plutarch hypothesized that rain followed military battles. This theory died hard; Napoleon believed volleys of gunfire could bring rain, as did the U.S. Civil War brigadier general, Joshua Lawrence Chamberlain. In the late 1800s, the U.S. Congress bankrolled a project to initiate rain over West Texas using an elaborate system of kites and homemade mortar. Despite somewhat promising early results, the effort was eventually deemed a disaster.

War played a role in WMI's genesis, too. After World War II, and the Korean War, many North Dakota–bred fighter pilots returned to the farm, only to have their crops ruined by a succession of hailstorms. As North Dakota farmers were pioneering ways to halt hail, the U.S. government, spurred into action by the Soviets — who were claiming great success using rockets to seed clouds — was initiating Project Skywater. From mountaintop stations across the Rockies, government scientists were spraying clouds with silver iodide. "We had just come out of World War II and felt we were on top of the world," says Boe. "We thought we could do anything, we could be Adam, and humanity had no bounds on what science could do."

During the 1960s and '70s the project, monitored by the National Science Foundation and the National Center for Atmospheric Research, continued in eastern Colorado as the National Hail Research Experiment. But after several summers scientists concluded there was no evidence their work was enhancing rain or reducing hail, and killed the project, which joined a long list of failed government weather mod schemes.

Despite Boe's aversion to the idea of weather modification, the term favored by the industry is "weather mod," and few people realize just how much the process may be affecting their lives. If you fly into Salt Lake City in winter, a weather mod company may have helped clear the fog that allowed your plane to land. If you water ski on Lake Mead in summer, weather mod may have helped to prime the clouds that poured the rain that meandered into the rivers to fill the lake. And if you are in Philadelphia or New York City and dare to eat a peach, or plum, or apricot, or nectarine, it may well have come from California's Central Valley, irrigated by water channeled from snowmelt on the Sierra Nevada mountain range, above which weather mod planes regularly fly, aiming to enhance snowfall.

Weather mod goes far beyond the borders of North America. WMI pilots have flown airplanes into thunderstorms on six continents. The company has worked to suppress hail in Argentina and Alberta, build snowpack in California and Wyoming, and enhance rain in Saudi Arabia, Turkey, Mexico, India, Morocco, and Mali. Typically, the company's contact is with government agencies or militaries, but not always. An unusual request came from lush Papua New Guinea, where a copper mine wanted WMI to help boost rainfall during the dry season in order to keep a steady flow in rivers that run the hydroelectric dams that power the mine.

Rain falls regularly from clouds onto our umbrellas and faces, yet rarely do we contemplate its dramatic journey. To do so, first erase your mental image of water. It is nothing but a loosely knit collection of H²O molecules, which we call a liquid. Ice is a tightly packed collection of H²O molecules — a solid — and a bunch of H²O molecules on their own constitutes water vapor, a gas. Sun-heated air and water vapor near the Earth's surface float up into the sky and cool while rising, the air condenses, and the H²O molecules are drawn closer together.

Water vapor cannot become liquid water without the help of tiny wind-blown particles in the atmosphere such as dust, soot, and salt. These particles serve as collection points, drawing water vapor molecules into a glob of water called a cloud droplet, the beginnings of a cloud. Still, cloud droplets are small, typically 5 to 10 microns across, and one must collide with a million other cloud droplets before becoming large enough to form the thing we call a raindrop.

In 1946, the atmospheric scientist Bernard Vonnegut, novelist Kurt's older brother, discovered that when compounds like silver iodide are dropped into clouds they act like the dust, soot, or salt and enable water vapor to cling to them, jump-starting the raindrop formation process. Rain can't be created from nothing, but clouds can be made more efficient at producing it, or so says the science of cloud seeding.

Ice crystals are formed in basically the same way as rain. Like the change from vapor to liquid, water is sluggish in its transition to ice, but again, particles in the atmosphere help draw liquid water in and lock it into place to become solid. The thinking behind hail suppression is that spraying silver iodide into a developing thunderhead — the birthplace of all hailstones — spawns an army of smaller ice particles that uses up the available cloud water, thus preventing the larger crop-crushing hailstones from forming.

Steffany Royal has turned her Piper Seneca around to flee the storm and its turbulence, but already racing toward the cell is colleague Vadim Alekseyev, 26, in a Cessna 340. He approaches from the south and finds a clear, less turbulent path to the edge of the storm. Here he spots what he's looking for, a shelf, or fluffy layer of clouds just below the base of the thunderhead. Alekseyev turns on his burners. And lo and behold, Royal is back. She follows Alekseyev's route into the storm, and switches on her burners. Alekseyev also unloads two burn-in-place flares, an extra bump of silver iodide.

The effectiveness of cloud seeding has been hotly debated. WMI's Boe points to evidence, published in reputable scientific journals, that indicates seeding clouds for snowfall enhancement can show a 5 to 15 percent increase in precipitation. But these assessments tend to be weighted down with caveats. A more thorough assessment entails lacing seeded clouds with a tracer that can later be detected in the actual rain or snowfall that makes it to the ground, but such projects are prohibitively expensive and still don't necessarily confirm that the precipitation would not have fallen anyway.

Measuring the success of hail suppression is just as difficult. "I'm not aware of any statistical evidence that it works," says Harold Brooks, a senior research scientist at the National Severe Storms Laboratory in Norman, Okla. "Mind you, it's very difficult to design and carry out experiments to test it." Perhaps the best analysis comes from Boe himself. "It is not a total solution, but it works," he says. "And it is comparatively cheap, and not doing it is so disastrous that our clients are happy to do it."