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A Hot Flash for Lightning Buffs

Scientists can now track all strikes globally

FRIDAY, Dec. 21, 2001 (HealthDayNews) -- It turns out that lightning does strike twice, or maybe even three or four times if you live in equatorial Africa.

That area has the most thunderstorm activity in the world, an astonishing 300 days annually, according to data sent down from a satellite to the lightning team at the National Space Science and Technology Center (NSSTC) in Huntsville, Ala.

This "eye in the sky" -- basically a high-speed camera -- allows scientists for the first time to track when, how often and precisely where lightning strikes all over the world.

Tracking lightning may also go a long way toward making people safer. In the United States, 1,318 people were killed by lightning between 1980 and 1995, according to the latest figures available from the Centers for Disease Control and Prevention.

This satellite technology is part of the government's goal "to try to better understand what the state of the earth is and what man is doing to it, part of a need to quantify global changes," says Hugh Christian, a physicist and group leader for the lightning team at NSSTC. Christian's team developed the sensing technology.

Down the road is even more sophisticated technology that will allow forecasters to get a jump on potentially severe storms, Christian adds.

Other findings from the satellite data that help give a global picture of weather patterns are that there is little lightning at the north and south poles or over oceans, and that Florida leads this country in the number of lightning strikes, followed by other coastal areas along the Gulf of Mexico, Texas, and Oklahoma.

A combination of temperature, topography and air flow from nearby water is what most affects when and where lightning strikes, according to Christian.

Warm temperatures trigger the most storm activity.

"Most storms are driven by heat. As the days get hotter, the weather becomes more unstable," he says.

In Florida during the hot summer months, for instance, sea breezes from the Atlantic Ocean and the Gulf of Mexico collide over the state and push the hot ground air skyward. When the hot air rises and meets the colder air, tiny ice crystals and water droplets are formed. For reasons not fully understood, electrical charges accumulate on these particles, creating electrical energy that eventually is released as lightning.

In Africa, year-round warm weather conditions, combined with the unique combination of mountainous topography and air flow from the Atlantic Ocean, mean that thunderstorm activity is almost constant.

"We were surprised at just how much activity there was over equatorial Africa. While most areas have seasonal thunderstorms, the meteorological conditions in the Congo mean they get thunderstorms all year round," Christian says.

Most storm measurements are now gathered by lightning sensors on the ground, which are accurate but are limited by location. Now the NSSTC's tracking devices, in orbit since 1995, record about 500 images a second as the satellites orbit the earth. The data they send back allow scientists to map storm patterns throughout the world, including less populated areas and oceans.

The satellites not only record the lightning strikes that hit the ground, which account for about 25 percent of all strikes, but they also can record far more extensively than the ground sensors the strikes that occur between clouds or within clouds, which account for most lightning activity.

The satellite being used for charting lightning is called the Lightning Imaging Sensor (LIS) and was launched in 1997.

They are the first steps toward technology that will be able to provide better information for weather prediction, Christian says. The NSSTC is now designing a new lightning detector called the Lightning Mapper Sensor (LMS), which will be able to sense high electrical activity so that forecasters can be alerted ahead of time to potentially severe storms.

"The data can be released as it is happening, so that severe weather warnings can be used by television stations or by golf courses," Christian says . He estimates that the technology will be ready in about four years.

Daphne Zaras, a meteorologist at the National Severe Storms Laboratory in Norman, Okla., says that her office uses radar data that delivers information about weather patterns every five or six minutes when there are storms. The orbiting satellites, she says, can only provide information every 12 hours, which means they are not useful at present for specific weather predictions.

"Often the question we ask in research is, 'How long will it take until it can be used practically?'" she says. "I would give this about five years."

What To Do

To see the colored map that tracks global lightning strikes, you can visit Science at NASA.

An informative history of lightning research is at this NASA lightning primer.

Here's an article from the Centers for Disease Control and Prevention on lightning strikes in the United States and how many people they kill.

For more fascinating facts, try the National Lightning Safety Institute.

SOURCES: Interviews with Hugh Christian, Ph.D., group leader for the lightning research team, National Space Science and Technology Center (NSSTC), Huntsville, Ala.; Daphne Zaras, meteorologist, National Severe Storms Laboratory, Norman, Okla.; photo courtesy of NASA
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