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Weather May Help Elevate Ozone Levels
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Published: May 15, 2008
TAMPA - Barring a change in weather, ozone levels could prompt more air quality advisories such as the one issued Tuesday.
On Tuesday, the cloudless sky, baking sun and lack of a sea breeze off the Gulf of Mexico pushed ozone levels in Hillsborough County to a record level.
A high-pressure area that's dominating the weather over Florida is creating an inversion, with warmer air layered atop cooler air near the ground. That condition prevents air from mixing and keeps pollution pinned to lower levels in the atmosphere.
Hillsborough County Environmental Protection Commission monitors registered an ozone level of 100 parts per billion over eight hours. That's the highest since the county started monitoring the eight-hour average five years ago, said Jerry Campbell, its director of air management.
A weak and crumbling cool front that could ease over the peninsula Friday may disrupt the inversion and bring a bit of rain that could help flush the sky.
It also could cause a wind shift that might bring smoke from the wildfires on the east coast over the Tampa Bay area. That smoke plume is drifting over Southwest Florida.
The change in wind direction might push the smoke that's hovering over the Gulf of Mexico back toward Hillsborough, said Tom Tamanini, chief of air monitoring.
Ozone, which can cause breathing difficulties for people with respiratory ailments or someone doing physically demanding work outdoors, forms when sunlight cooks nitrogen oxide and converts it into ozone.
The nitrogen oxide comes from pollution such as exhaust from cars, power plants and manufacturing.
The high temperatures and lack of clouds that have been a staple of weather the past weeks are an ideal combination for creating ozone.
"When the sky is crystal clear and it's this hot, it creates a pressure cooker for ozone," Tamanini said.
Federal regulations that went into effect this year lower the level of ozone that triggers an air quality advisory. The county must issue an advisory when ozone levels top 75 parts per billion averaged over eight hours.
The change has prompted Hillsborough County to put out five advisories this year compared with four in all of 2007.
Campbell said three of the advisories put out this year would not have been issued under old regulations that required an advisory when ozone reached 84 parts per billion.
"The air quality isn't getting worse," he said.
He said the east coast fires may have contributed to Tuesday's record level even if smoke didn't directly flow over Hillsborough County.
The fires that have burned more than 15 square miles dump a lot of nitrogen oxide into the atmosphere, the raw material for ozone.
"We'll be looking at that, and so will the state," Campbell said.
Even if the weekend disrupts the weather pattern that's helping create the ozone, the scenario could return by next week. Forecasters do not see a major change in the weather pattern until the rainy season begins, usually in the second week of June.
"The situation may re-create itself," Tamanini said.
Reporter Neil Johnson can be reached at (813) 259-7731 or njohnson@tampatrib.com.
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