A new study has suggested that dust pollution in the atmosphere may push supercell thunderstorms into spawning tornadoes.
According to a report in Discovery News, the study was done by David Lerach of Colorado State University and a team of researchers, who compared two computer models of supercell storms.
While one model had a clean atmosphere, the other was riddled with microscopic dust particles.
In the clean model, the telltale rotating cloud formed, but no twister ever materialized. In the polluted version, which had 10 times more dust, it did.
Lerach believes that the abundance of microscopic particles prevents water from condensing into raindrops big enough to fall to Earth.
Rising warm air lofts the miniature droplets high into the cloud where they freeze instead. This leaves the air currents that are the precursors to tornadoes free to swirl beneath the cloud.
"In the clean case, all the rain washed out the core of the storm and killed the downdrafts," Lerach said.
Though scientists still don't understand tornado formation very well, they generally believe cold downdrafts, also called gust fronts, that mix with rising warm air underneath a storm, are crucial to whipping up tornadic winds.
Aerosol pollution can come from natural, as well as man-made sources.
It's possible that the aerosols humans produce from their cars, factories and power plants could also increase tornado formation.
According to Lerach, "The model suggests if there's more crap in the air, tornadoes are more likely to form. It raises interesting questions about the role of air pollution and aerosols in tornado genesis."
"You'd want to do a field study looking at aerosol concentrations in a sparsely populated, relatively clean area, and then look downwind of a major city to see if there's any difference in tornado formation," said Nathan Snook of the University of Oklahoma.
"It would also be interesting to see if aerosols emitted from dust storms are going have a different effect on thunderstorms than human-emitted aerosols," he added.