Scientists in Pursuit : Thunderstorms: On Your Mark, Get Set, Go . . .

Although most Americans would rather avoid thunderstorms, a team of scientists is seeking them out and sending up instrument-loaded balloons in hope of learning what makes the storms work and how to better predict them.

Measurements of the overall electricity in the storms, and the charge on individual rain particles, could help scientists understand the differences in behavior between large and small storms, said W. David Rust of the National Oceanic and Atmospheric Administration.

That, in turn, can help in predicting what the storms will do and in issuing warnings, Rust said in a telephone interview from the National Severe Storms Laboratory in Norman, Okla.

Rust said the effort gets under way “at the next storm which, if we’re lucky, will be tomorrow.”

He will lead a seven-man team in a pair of vehicles, chasing the huge storms that sweep across the middle of America hammering away with lightning and tornadoes.

He and Tom Marshall of the University of Mississippi launched the project last summer, Rust said, following up studies of small storms Rust had done in New Mexico.

Two types of balloons are being used this year--small 4-foot diameter balloons with instruments to measure the general electrical field in the storm, and larger 6- or 7-foot versions to measure the charge on individual raindrops.

Studying Structure

“Measurements like that have never been made in severe storms,” Rust said. “We’re trying to understand the electric structure of thunderstorms, in particular severe thunderstorms. . . . We want to know if they are significantly different from small thunderstorms or not.”

The large storms have some unusual lightning characteristics, he explained, and the scientists want to know if that is tied into the rainfall patterns of the storms, which is one reason they want to measure the electrical charge on raindrops.

Severe storms tend to have a much higher share of intra-cloud lightning than smaller storms, Rust explained, adding that this seems to be associated with intensification of the circulation in the storm and possibly with formation of tornadoes.

In addition, the severe storms sometimes produce lightning strikes to the ground with a positive charge, rather than the negative charge more commonly found in lightning, he said.

Rust said he hopes the work will help lead to better forecasts, “bridging the gap between basic ivory-tower research and applications.”

Few would confuse his workplace with an ivory tower.

When a storm is reported, the team sets forth in a van and truck in pursuit. The truck carries an already-inflated balloon in a box structure, while the van has been gutted and refitted with an array of instruments.

Balloon Set Free

Chasing down the storm, they try to locate the area under the towering anvil cloud to set the balloon free.

The balloon is pulled into a large plastic tube to help hold it steady until release. The team has released balloons in winds of more than 50 m.p.h., and the team usually has to drag it, in the tube, away from trees and electrical wires. Once aloft, the balloon is tracked by radio instruments.

Yes, Rust admits, lightning can interfere with the signals sometimes, though most data gets through.

And some balloons become casualties of a trip into the storm, he conceded.

Last year, when the research was started, one balloon disappeared “in conjunction with a lightning flash” in the cloud, Rust said. Others have been battered back to the ground by hail swirling around in the storm. But most make it through, he added, sending back information along the way.

There can be too much lightning, though. Rust admits having scrubbed a few launches last year when he considered it too dangerous.

He does not mind when people liken his research to Benjamin Franklin, who pioneered lightning studies with a kite.

But he also knows that Franklin was lucky. Others trying to duplicate the kite-flying experiment have been killed by electrical storms and Rust does not want his team to join them.

“We are very cautious when releasing a balloon in a storm environment . . . We try to use good judgment,” Rust said.