Pollution could spawn tornadoes

Dust particles pumped out by industry, agriculture and transport could be the catalyst that makes a nasty thunderstorm switch into a spawning ground for tornadoes.

Researchers from Colorado State University who have been seeking a greater understanding of the twisters that plague the American Midwest each year believe that particulate matter could be partly to blame for the devastating problem.

Their research was based on computer modelling rather than field observations and sampling and could shed some light on the mystery of why some so-called supercell thunderstorms blow themselves out while others crank up the extreme weather a notch and generate twisters which rip through the landscape.

The team compared two computer models – one with clear air and the other with a high level of fine particulate matter.

In the clear-air model, tornadoes never quite formed, while in the pollution-heavy model, they did with some frequency.

David Lerach, leader of the research team, admits it is still unclear as to why exactly this might be but says it could be that the dust prevents water in the atmosphere from condensing into big enough droplets to fall as rain, thus stopping the storm from breaking.

Instead of falling as rain, he believes that warm air carries the tiny water droplets high into the cloud where they freeze and this process effectively leaves the way clear below for the rotating air currents that are the precursor to tornadoes.

Sam Bond

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