Thunderstorm aficionados, if you really want to see some action then get yourself aboard a cargo ship. A new study has shown that lightning strikes occur nearly twice as often above busy shipping lanes than in the regions to either side. It turns out the belching fumes from ship exhausts are helping to trigger extra lightning.
While analysing data from the Worldwide Lightning Location Network, a web of sensors around the world that track lightning strikes, researchers noticed nearly straight lines of lightning strikes across the Indian Ocean and South China Sea.
By comparing the lightning data with maps of ships’ exhaust emissions they were able to show that there were nearly twice as many lightning strikes along the main shipping routes between Sri Lanka and Sumatra, and between Singapore and Vietnam. This enhanced level of lightning was visible at least as far back as 2005.
Writing in Geophysical Research Letters, the researchers explain how the ship exhaust fumes add more particles to the air, which encourages more cloud droplets to form. Because the cloud droplets are smaller and lighter than they would otherwise be they travel higher into the atmosphere and are more likely to reach the freezing line, so creating more ice particles. Collision between ice particles causes storm clouds to electrify, and lightning is the atmosphere’s way of neutralising the built-up electric charge.
“It’s one of the clearest examples of how humans are actually changing the intensity of storm processes on Earth through the emission of particulates from combustion,” said Joel Thornton, from the University of Washington, in Seattle, the lead author of the study.
