Venezuela’s Lake Maracaibo is the world’s hot spot for lightning.
If you don’t want to get struck by lightning, avoid open areas and tall objects, as the experts suggest. But if you want to be extra safe, stay the heck away from the middle of Venezuela’s Lake Maracaibo. Satellite data suggest that one particular square kilometer there—on the northern tip of South America—gets zapped more than 200 times per year.
“Lake Maracaibo is one of the largest lightning generators on the globe,” says Robert Holzworth, an atmospheric physicist at the University of Washington in Seattle who was not involved in the new study.
The find comes from instruments on a satellite called the Tropical Rainfall Measuring Mission, which operated from 1997 to 2015. Circling the planet on a path that covered every spot between 38°N (about the latitude of Athens) and 38°S (just south of Melbourne, Australia), it could view a square about 600 kilometers on a side (an area almost the size of Montana) at once, says Rachel Albrecht, a meteorologist at the University of São Paulo in São Paulo, Brazil. The craft passed over each spot in that broad swath between three and six times per day, viewing it for about 90 seconds each time, she notes.
Albrecht and her colleagues divvied up all lightning flashes spotted between January 1998 and December 2013 into areas roughly 10 kilometers on a side or smaller. Then, they tallied the planet’s top 500 hot spots for lightning, based on flashes observed per square kilometer per year. (Because the satellite could observe each spot only 10 minutes or so each day, the hottest of the hot zones are likely struck by lightning tens of thousands of times each year, data suggest.) The hard data gathered by this space-based survey confirm many of the general trends that meteorologists have long noted, the researchers say.
The world’s top 100 hot spots for lightning (including the top one on each continent, labeled) at latitudes below 38°N, as measured by satellite between January 1998 and December 2013.
CREDITS: (GRAPHIC) J. You/Science; (DATA) Albrecht et al., Bulletin of the American Meteorology Society (2016)
In general, lightning occurs more frequently over land than over the oceans, in summer more than in winter, and most often between noon and 6 p.m. local time. Each of these factors tends to increase the temperature difference between the air at ground level and layers at higher altitude, which in turn increases the amount of humid air rising to fuel thunderstorms. Yet exceptions to these general rules abound, and the Lake Maracaibo hot spot bucks all three trends: Most of its lightning occurs over the lake, between the hours of midnight and 5 a.m., and in late spring and autumn. All told, the satellite spotted about 233 flashes of lightning per square kilometer per year over one portion of the nearly Connecticut-sized lake, the researchers report this month in the Bulletin of the American Meteorology Society.
Many of the world’s lightning hot spots are associated with steep terrain, which helps set up the clash between warm and cool air masses that can drive thunderstorm development, Albrecht says. The top hot spots on each continent, with one exception, are near steep mountains, the researchers note. That’s certainly true of Lake Maracaibo, which is rimmed by lofty peaks; the clash between the cool winds flowing off those mountains at night and the lake’s warm tropical waters creates thunderstorms over the lake about 297 nights each year. Indeed, the researchers note, lightning over the lake at night is so reliably persistent that early explorers sailing the Caribbean used its flickering as a navigational aid.
At least 14 other large lakes worldwide, including lakes Victoria and Tanganyika in Africa, are also lightning hot spots, says Steven J. Goodman, an atmospheric physicist at the National Oceanic and Atmospheric Administration in Greenbelt, Maryland, and co-author of the new study. Though Lake Maracaibo is the hottest spot of all, central Africa is still home to the broadest area afflicted by lightning, with 283 of the world’s top 500 locales. Although many sites with latitudes above 38°N experience thunderstorms, they do so far less often than low-latitude regions and typically only during half the year, unlike tropical areas where they can strike year-round, Goodman says. So, it’s not likely that the team’s new study missed any of the world’s top lightning hot spots.
Source: Science Mag