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Where lightning strikes most, and how lightning forms

Q: Where in the world do the most lightning strikes occur? What position is South Africa in the list? (Jabulani, Johannesburg, South Africa

A: Each year, lightning flashes about 1.4 billion times over Earth. This movie taken from the Space Shuttle Columbia shows Argentina under fire. Hundreds of strikes flash along the storm’s 580-mile (930 km) front like a scene from a war picture.

Lightning zaps within the cloud, from cloud to cloud, and from cloud to ground. Only about 30% of all discharges go from cloud to ground, says E. Philip Krider, professor of atmospheric sciences at the University of Arizona.  Courtesy of NOAA

For most landmasses, lightning strikes most often during the summer. That, of course, limits the strikes. Not so in equatorial Africa — where summer is year round, and lightning is a way of life. The spot with the most lightning lies deep in the mountains of eastern Democratic Republic of the Congo near the small village of Kifuka (elevation 3200 feet, 970 m). Thunderbolts pelt this land.

In a year, 158 bolts occur over each square kilometer (10 city-blocks square), says atmospheric physicist Steve Goodman of NASA’s Global Hydrology and Climate Center (GHCC) in Huntsville, Alabama.

The black dot (in the middle of the largest white area in Central Africa) marks the spot — near the tiny town of Kifuka in the Democratic Republic of the Congo — where the greatest lightning activity in the world occurs. The color code at the top of the image shows the number of flashes per square kilometer during the year. Note that over the oceans and desert "white" means no lightning. [Courtesy of NASA’s Lightning Imaging Sensor (LIS) Instrument Team and the Global Hydrology Resource Center (GHRC).]

Your homeland in South Africa doesn’t come close. The greatest flash density averages only 36 discharges per square kilometer per year — only 23% of Kifuka’s rate, says Goodman. This rate occurs at Costmore, located about 85 miles (135 km) west of Durban, in southeastern South Africa.

Where lightning strikes Earth. Please click here for a higher-resolution map. Courtesy of NASA’s Lightning Imaging Sensor (LIS) Instrument Team and the Global Hydrology Resource Center (GHRC).

We can see how South Africa ranks in the lightning race by checking the world map of strikes averaged from April 1995 to February 2003. It does rank in the top 4^th category (orange-red) but the world is full of similar spots.

By the way, here’s how various continents rank according to Goodman:

NASA’s Lightning Imaging Sensor Instrument Team and the Global Hydrology Resource Center (GHRC): A map that shows where lightning hits over Earth

NASA Global Hydrology and Climate Center: Observing lightning from space

NASA Global Hydrology and Climate Center: Lightning detection from space: A lightning primer

NOAA: Flash facts about lightning

Q: What causes lightning? (Lanney, Sandia Park, New Mexico)

A: Within the maelstrom of a thunderstorm, lightning is born. Ice and supercooled water are the keys to the process, says E. Philip Krider, professor of atmospheric sciences at the University of Arizona. Violent winds buffet tiny hailstones as they form, causing them to collide. When the hailstones hit ice crystals, some negative ions transfer from one particle to another. The smaller particles lose negative ions and become positive and the larger more massive particles gain negative ions and become negative.

Lightning discharges an excess of positive and negative charge within clouds, between clouds, or between clouds and the ground. Drawing adapted from lightning article by Ron Hipschman.

"Ions (both positive and negative) have a lower mobility and a longer lifetime than free electrons," notes Krider. So, the charges on the ice particles tend to persist.

"The strong updrafts within thunderstorms carry the smaller positively charged ice particles to the upper regions of the cloud while the larger, heavier negatively charged (hail) particles collect in the lower and middle portion of the cloud,"says atmospheric physicist Steve Goodman of NASA’s Global Hydrology and Climate Center (GHCC) in Huntsville, Alabama.

This creates charge differences, like that between the terminals of a car battery. When the potential difference between the regions gets too great, lightning flashes, heating the discharge channel to sun-surface temperatures. The air expands explosively, forms a shock wave, and thunder cracks — nature’s sonic boom.

Further Reading

Wikipedia: Lightning

Lightning by Ron Hipschman

Benjamin Franklin and the first lightning conductors by E. Philip Krider

(Answered Dec. 13, 2005)