NASA leads effort to crack mysteries of lightning

Lighting is more common in storms over land than over oceans, prefers afternoons and varies from one season to the next.

June 22, 1999
Web posted at: 1:28 p.m. EDT (1728 GMT)

Between 1959 and 1994, 3,239 people were killed by lightning strikes and 9,818 people were injured. Understanding how and why lightning occurs may help scientists offset some of the estimated $35 million in annual losses due to the weather phenomenon.

At a recent conference on lightning in Guntersville, Ala., NASA-sponsored scientists presented findings on global lightning patterns garnered from instruments that provide a view of lightning from above the cloud tops.

"It does look like lightning is sensitive to changing weather patterns that evolve from year to year," said Hugh Christian of the Global Hydrology and Climate Center in Huntsville, Ala.

According to their findings, lighting is more common in storms over land than over oceans, prefers afternoons and varies from one season to the next.

"Over land we see tremendous diurnal changes, a strong peak in lightning in the afternoon over land," said Christian. "Over water we see very little variation. We believe it's due to the land absorbing heat and causing strong convection. On the other hand, water can store a lot more heat, and release it slowly."

The scientists also reported that lightning appears to follow the sun. "As summer in the northern hemisphere progresses, you see lightning moving farther north. You see a similar pattern in the southern hemisphere, but not so pronounced because there isn't as much land outside the tropics," said Christian.

Variations in lightning patterns show up from one year to the next. Christian is currently analyzing data that hints lightning patterns are influenced by the El Niņo and La Niņa weather patterns. He said this evidence shows that global lightning patterns may be one way to take the pulse of the planet's weather trends.

"We can use lightning to monitor and study storms, including severe thunderstorms," he said. Lightning can only be generated by convection within a cloud system. "It's tightly coupled with the dynamics and physics of the storm. We use it to monitor its evolution and life."

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