Flashes sizzle in the South.

Flashes sizzle in the South

On average, a lightning stroke in Florida packs almost twice the electric current of one in New England, reports Richard E. Orville from the State University of New York at Albany. He made the discovery as he analyzed the peak current in more than 5 million lightning flashes recorded during 1988 by 36 instruments in the eastern United States. The instruments are part of the National Lightning Detection Network, which Orville and others began organizing in 1982.

Orville's study concentrates on the peak electric currents flowing through the first return stroke, which travels from the ground up to the cloud. He found that the mean peak currents in New England measured around 25,000 amperes, compared with 40,000 to 45,000 amps in northern Florida. The study is the first to show that characteristics of lightning flashes vary as a function of latitude, asserts Orville in the Jan. 11 NATURE. He suggests equatorial lightning strokes might carry even higher peak currents than those measured in Florida.

As one possible explanation for the variation, Orville proposes that cloud volume may play some role. Observations have revealed that Florida's summer cumulonimbus clouds generally measure about 30 percent taller than those in New England. Their greater volume may allow these clouds to store more charge and generate more powerful currents, Orville says.