Rain Man

Snow, sleet, hail or volcanic eruption cloud physicist Peter Hobbs will find a way to fly into it

Peter Hobbs leans toward me as if to shout over the roar of the bucking Convair 580 turboprop airplane when there’s a tremendous bang, and a burst of orange fire flashes across the sky outside my window. I brace for a death spiral. Hobbs cracks a rare grin. "We just got hit by lightning," he announces with obvious delight.

As founder and head of the University of Washington’s Cloud and Aerosol Research Group, Hobbs has spent the better part of a lifetime flying into some of the most horrendous weather conditions on the planet in a quest to understand the highly complex dynamics of snow, rain, sleet and hail.

Precipitation remains one of the great mysteries of the natural world. Difficult to predict accurately more than a day or two in advance, invisible in its origins, chaotic in its behavior, wet weather is only just beginning to yield its secrets to Hobbs and other scientists. The main puzzle, of course, is what causes it in the first place. Hobbs has spent nearly 40 years trying to figure this out and, in the process, has helped to forge the field of cloud microphysics. "To forecast precipitation—where and when it will form and at what intensity—you need a good understanding of the small-scale processes within clouds," he says. Better forecasting could enable farmers to harvest crops before they are damaged by hail or rain. Townships plagued by flooding could gain precious time to make preparations.

With his British accent and buttoned-down demeanor, Hobbs, 66, looks more like a Fleet Street banker than a daring adventurer. But it’s clear that he shares a fierce dedication to his work. "In the old days," Hobbs says, "we’d apply gooey stuff to a stick and hold it outside the plane’s open window until crystals formed on it. Then we’d pull it back into the plane, take it down, and analyze the crystals one by one under a microscope." Now, the Convair is jammed with more than $1 million worth of specialized equipment, including a Cloud Particle Imager (CPI), which has a digital camera that snaps 40 frames a second of ice crystals as small as ten microns, about one-tenth the width of a human hair.

As the aircraft continues to bounce through a storm at 15,000 feet over Washington State’s coast, Hobbs stares at shapes resembling four-leaf clovers, fish tails and muffins dancing across the screen of his laptop—real-time renderings of the ice particles outside the aircraft. These are proto-raindrops, Hobbs explains, the seeds in upper reaches of clouds that, under the right conditions, will mass together to form small hailstones (known as graupel). When graupel falls from clouds and hits warmer air, it melts and creates raindrops. "At present, forecast models don’t take into consideration what happens within the clouds," says Hobbs, "and that’s what we’re hoping to improve by studying how tiny cloud particles grow, and what role ice and snowflakes play in various types of weather systems."

Hobbs’ fascination with weather started when he was a child in post-World War II England. Born in the London suburb of Richmond in 1936, Hobbs was evacuated to the north of England in 1943, and he says his education was pretty sketchy until he returned home at war’s end two years later. "My parents were despairing of me," he recalls. Trying to rouse his interests, they sent him into London one day to visit an aunt who worked for the United Kingdom Meteorological Office. "She got the weather observer to take me onto the roof and show me how to make measurements using a psychrometer, anemometer and rain gauge. I was fascinated," he says. "Soon I had built my own weather station."

By the time he was 14, Hobbs knew he wanted to devote his life to investigating the elements. After attending a lecture on the physics of rainmaking by Sir John Mason, he approached the eminent British atmospheric scientist for career advice. "'You’re a bit young,' Mason told me. 'Come back and see me when you have a degree in physics.' Ten years later I knocked on his door with my physics diploma from Imperial College in my hand. He took me on as a graduate student on the spot."

After receiving his PhD for research in cloud physics in 1963, Hobbs came to the University of Washington in Seattle as an assistant professor. He chose Seattle, he says, because it is the "cloud capital of the world."

Frustrated by having to conduct weather research from a subbasement lab on the University of Washington campus, Hobbs wangled a trip for himself and a team of graduate students to fly to a glacier on 7,965-foot-high Mount Olympus, where they could study clouds up close. That experience hooked him on the idea of using airplanes as mobile laboratories. By 1970 he had secured the use of a Douglas B-23 Dragon, a World War II-era patrol-and-training aircraft that had been owned by Howard Hughes and had seen action in war movies. The plane, bought by the university and supported by federal grants, gave Hobbs the freedom to investigate whatever weather phenomena piqued his curiosity, from the sulfur content of Arctic haze and the structure of ice crystals in Pacific winter storms, to the meteorological fallout of the more than 600 oil wells burning in Kuwait after the Gulf War.

Over the past 32 years Hobbs has circled the globe on three different aircraft he’s outfitted with a raft of meteorological instrumentation, attempting to learn why precipitation arrives in distinct rainbands, how pollution affects rainfall, and the nature of the relationship between cloud processes and rainfall intensity.

Hobbs' customary reserve cracks again when he recounts a mad dash into the scalding plume of Mount Saint Helens as it spewed ashes several miles into the atmosphere on the morning of May 18, 1980. The volcano blew at 8:20 A.M. on a Sunday, and by 11 A.M. Hobbs and his crew were in the air and flying toward it.

"As we approached this monster, I could see that the huge plume looked like a cauliflower with each part heaving and turning," he recalls. As they flew 20 miles downwind, a volley of explosions suddenly rattled the plane. "I remember thinking we’re being hit by rocks and we’re dead," he says. "But it turned out to be volcanic hailstones—highly charged conglomerations of dust that fell apart when they hit the plane."

The noise was terrifying, but the aircraft sustained no significant damage. As the plume drifted into Idaho, Hobbs recorded some of the first quantitative measurements ever made of the carbon dioxide, water vapor and sulfur dioxide emitted by an erupting volcano.

Given his passion for flying into billows of smoke, volleys of volcanic hail and torrents of microscopic ice crystals, I was surprised to learn that the Convair had recently been sold. "I’ll miss the excitement of doing fieldwork all around the world," he says. But he won’t miss having to raise $2 million each year, most of it in grants, which he needs to fund his aerial projects.

Even so, Hobbs is adamant that he has no intention of coming in out of the rain. After all, he has accumulated enough data to keep him and his department squeezing secrets out of the clouds for at least the next ten years.

Get the latest Science stories in your inbox.