Aerosols are the smallest form of airborne pollution, at less than 50 nanometers wide, but they can double the destructive power of a severe storm, researchers have found.
Atmospheric scientists had previously discounted the tiny particles’ influence in cloud formation, focusing instead on the way water vapour condenses on much larger motes of dust or biomass.
But in Manaus, Brazil, investigators found what InsideClimate News calls “an ideal test bed” to give aerosols another look. The city of two million people is bounded on one side by more than 1,000 kilometres of rainforest, on the other by airborne pollution plumes from its booming industrial parks.
The researchers found that when aerosols enter the air columns occupied by “deep convective clouds”—better known to casual observers as thunderclouds—they provide nuclei for the condensation of water vapour into droplets, dramatically speeding up the process and revving the cloud’s kinetic potential.
“The large surface area at the top of the clouds can become oversaturated with condensation,” ICN reports, citing the researchers’ paper in the journal Science. This “can more than double the amount of rain expected when the pollution is not present.”
“It invigorates the storms very dramatically” by a factor of 2.5, said lead author Jiwen Fan.
One of the untested ideas promoted by enthusiasts of geoengineering is the large-scale injection of additional aerosols into the atmosphere, where they could reflect additional solar radiation and theoretically cool the Earth.