Delayed Test Blaze Finally Touched Off

After months of delays caused by bureaucratic bickering, bad weather and a helicopter crash, scientists Friday finally set more than 500 acres of brush ablaze in the mountains north of Los Angeles and unlimbered an unprecedented array of instruments to collect data from the resulting plume of brown smoke.

The data from the $750,000 project will be analyzed for study of phenomena ranging from fire-caused erosion and air pollution to the apocalyptic theory of “nuclear winter,� which holds that smoke from fires burning after a nuclear war would block sunlight and chill the Earth.

The fire did not burn as intensely as had been hoped because the brush was still damp from recent rains, but Philip Riggan, the U.S. Forest Service scientist in charge of the project, said the data gathered by five aircraft and a variety of devices on the ground would keep scientists busy for many months.

Watch From Ridges

Nearly 300 firefighters and scientists from more than a dozen government agencies watched from ridges and mountaintops Friday morning as a helicopter from the California Department of Forestry swooped into Lodi Canyon, a rumpled expanse of chaparral in the Angeles National Forest above La Verne, to touch off the fire.

A helicopter crashed on the same mission during an aborted attempt to set the fire Dec. 3, and this time the fire was ignited more slowly and cautiously.

The helicopter at first tried to start the fire by seeding the brush with small plastic spheres, virtually indistinguishable from Ping Pong balls, filled with explosive potassium permanganate. But when the fires caused by the incendiary devices failed to spread, the crew went back to the tried-and-true “helitorch,� a canister that dribbled a flaming trail of jellied gasoline as it was towed over the canyon.

A team on the ground used a hand-held torch to squirt flaming gasoline on the brush.

Take Samples of Air

Another helicopter, equipped to catch samples of air, flew a few hundred feet above the bright orange flames that erupted from the canyon walls.

A converted U-2 spy plane circling 65,000 feet overhead sent detailed images of the fire from a $600,000 infrared camera to scientists gathered in a trailer atop a nearby mountain.

Two airplanes equipped with “gulp samplers� and other gear flew repeatedly through the smoke plume, collecting samples of smoke particles and gases. These craft will “chase� the dispersing plume downwind today and Sunday, said Bernard Zak, an atmosphere scientist from Sandia National Laboratory in New Mexico, which provided one of the planes.

Frank Weirich, a UCLA geographer who studies erosion caused by fires, said that 10 temperature-sensing instruments that had been buried in the canyon before the fire was started seemed to be functioning well. Each of the $3,000 instruments recorded temperatures above and below the surface of the soil. The sensors will be retrieved over the next few days and will provide data on the relationship between the temperature of a fire and subsequent erosion.

Not Fierce Enough

Craning his head to look at the billowing plume of smoke, Richard Turco, the scientist who helped originate the “nuclear winter� theory and who is credited with coining the phrase, said that the fire did not burn as fiercely as he would have liked. He and other nuclear winter researchers had hoped that a large updraft of hot air would “punch through� the still air above the canyon and send smoke as high as 15,000 feet.

But because a layer of warm air created an atmospheric inversion above the mountains, the broad column of smoke flattened out at about 8,000 feet and trailed off to the east.

Turco, an atmosphere scientist at the Marina del Rey think tank R & D Associates, stressed that the fire in Lodi Canyon and other experimental fires that scientists hope to conduct to test this controversial hypothesis must be put into perspective. “What you see today is just one-millionth of the amount of smoke that would be produced in a full-scale nuclear war,� he said.

Riggan said that he and Turco plan to collect the results of the myriad projects and have them published in a special issue of the Journal of Geophysical Research.