Ozone tongues lick landscape

A Canadian study shows that tongues of ozone often descend to the surface of the earth, doubling the ozone levels overnight. So far this has been observed only in Eastern Canada. The project is currently in limbo, awaiting further funding.

scientists say the intrusions of ozone from the upper atmospheric can make significant contributions to smog and air quality.

Turbulence generated by winds racing through the upper atmosphere is believed to cause the ozone to drop down. “It’s like waves breaking on a beach,” says Tarasick, explaining how giant airwaves can break about 10 kilometres above the ground in the zone that separates the upper and lower atmosphere. The scientists say turbulence generated as winds speed over the mountains in Western Canada also generates intrusions.

The distinct tongues of stratospheric ozone often dissipate before they hit the ground, but [co-author David] Tarasick says they still can change air quality at street level. He estimates about 20 per cent of ozone at ground level originates in the upper atmosphere.

Sometimes, the research indicates it can be much higher. On May 3, 2005, the team picked up a giant ozone intrusion high in the atmosphere over Montreal. Four days later the stratospheric ozone reached the ground and ozone readings in the city almost doubled, from 15 parts per billion to 30 ppb at night and from 30 ppb to 50 ppb during the day.

Here’s a link to a PowerPoint poster of the research results. And here’s a link to ozone basics.


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