Thunderstorms directly above the busiest shipping lanes are
significantly more powerful than the storms in areas of ocean where ships do
not navigate, according to a new University of Washington research.
The study published Sept. 7 in
Geophysical Research Letters found that particles from ship exhaust make cloud
droplets smaller lifting them higher in the atmosphere thereby resulting ice
particles which leads to more lightning. This is the first evidence that humans
are changing cloud formation almost on a nearly continual basis. Cloud
formation can affect rainfall patterns and alter climate by changing how much
sunlight clouds reflect to space.
Its 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 lead author Joel
Thornton, a UW professor of atmospheric sciences.
All combustion engines emit exhaust,
which contains microscopic particles of soot and compounds of nitrogen and
sulfur. These particles, known as aerosols, form the smog and haze typical of
large cities. They also act as cloud condensation nuclei the seeds on which
clouds form. Water vapor condenses around aerosols in the atmosphere, creating
droplets that make up clouds.
Cargo ships crossing oceans emit exhaust
continuously and scientists can use ship exhaust to better understand how
aerosols affect cloud formation.
Co-author Katrina Virts, a former UW
postdoctoral researcher who is now an atmospheric scientist at NASA Marshall Space
Flight Center in Huntsville, Alabama, was analyzing data from the World Wide
Lightning Location Network, a UW-based network of sensors that locates
lightning strokes all over the globe, when she noticed a nearly straight line
of lightning strokes across the Indian Ocean.