Every second, as many as 100 lightning bolts strike the Earth. Now, a new map reveals a tally of those flashes over the last two decades, tracing where they strike the planet each year.
The data reveal that lightning is more likely to strike land than water, and these flashes occur more on land close to the equator. But the different intensities also reveal subtle differences in the storms themselves.
In 1998, NASA launched a Lightning Imaging Sensor on board its Tropical Rainfall Measuring Mission satellite. It was originally planned to be a three-year-mission, but the satellite is still up and running 17 years later. A second instrument, called the Optical Transient Detector on the OrbView-1/Microlab satellite, also collected data from 1995 to 2000, and recorded all flashes above the 38th parallel north latitude.
Roughly 90 percent of the lightning strikes on Earth occur between the 38th parallel south and 38th parallel north latitudes, said Daniel Cecil, a member of the Global Hydrology and Climate Center's lightning team.
But even on equatorial land, lightning strikes vary with different types of thunderstorms. Brazil commonly experiences large thunderstorms; the number of lightning strikes per storm, however, is relatively low, with only a few flashes per minute, Cecil said. But in places like northern Argentina, or even in the central United States, rare storms bring tens or hundreds of flashes per minute, he added.
The researchers are planning to send a lightning imaging sensor to the International Space Station and to geostationary orbit, where it will be able to continuously monitor certain spots on the planet, and therefore track certain storms.