ECLAIRS. This is an original – and rather disturbing – study. what has just been published Geophysical research letters. The lightning is twice as numerous where the merchant ships pass en masse. The phenomenon is particularly visible on the two busiest maritime routes, from India to the Strait of Malacca (Indonesia) which separates Malaysia and Indonesia and between this strait and the Chinese ports. The Strait of Malacca thus sees 100,000 boats pass through each year. It was Katrina Virts, an atmospheric scientist at the NASA center in Huntsville, Alabama, who first noticed in 2005 that lightning struck twice as hard on a line across the Indian Ocean between Sri Lanka and Malaysia. Storm activity is also one of the most intense in the world over the Strait of Malacca. These findings come from Worldwide Lightning Location Network WWLLN managed by Washington State University in Seattle (USA). The site even offers to see in real time where the lightning strikes!
Pollutants that cause more and smaller water droplets
CRYSTALS. From 2005 to 2016, observations of 1.5 billion flashes confirmed the permanence of the phenomenon. The study carried out by Joël Thornton, of the University of Seattle simply consisted of matching these observations with the map of the maritime routes, which can be seen very well. traffic thanks to GPS ship locations.
This infographic produced by the English organization UCL Energy Institute retraces the year 2012 of maritime transport
And these two pieces of information fit together perfectly. There is indeed a link between the merchant navy and storms. Container ships, freighters and bulk carriers induce twice as much lightning as in neighboring areas free of ships.
The first map shows the annual average lightning density as recorded by the WWLLN. The map below is that of aerosol emissions from ships since 2010 on the Indian Ocean and South China shipping lanes. © Thornton et al/ Geophysical research letters/AGU
The explanation given by the researchers is relatively simple. Updrafts from storms throw water droplets into the upper atmosphere that freeze. It is the friction between these ice crystals that generates electricity. Lightning is therefore an indicator of the strength of a storm, a phenomenon of great magnitude, however, coming from the microphysics of cloud formation and the interaction of billions of tiny grains of ice between them. In atmospheres with few aerosols like those of the oceans, cloud-forming water droplets are large and few in number. But on the sea routes, ships emit huge quantities of soot and nitrogen and sulfur compounds, the fuel used being always of poor quality. These particles cause the formation of smaller and more numerous micro-droplets which will provide a greater number of ice crystals in the upper atmosphere, therefore more friction, more electricity and more lightning.
«This is one of the clearest examples of how humans are currently changing the intensity of storm formation processes through their particulate emissions. “says Joel Thornton in a press release from the American Geophysical Union (AGU). The authors of the study point out that the formation of clouds is a phenomenon that is still very poorly understood. The disruption of what still constitutes a “black box” in the knowledge of the mechanisms governing the atmosphere and climates might therefore have consequences that no one is able to anticipate.
