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Philly ozone forecasts courtesy of Penn State student

Alexandria Herdt grew up in South Jersey, watching her young cousin wheeze and cough when ozone levels climbed high. "It hurts when you know there's really nothing you can do to help," said Herdt, 22, of Chesterfield, Burlington County.

Alexandria Herdt, who developed a model for predicting ozone levels while at Penn State, will continue her studies at Texas Tech.
Alexandria Herdt, who developed a model for predicting ozone levels while at Penn State, will continue her studies at Texas Tech.Read more

Alexandria Herdt grew up in South Jersey, watching her young cousin wheeze and cough when ozone levels climbed high.

"It hurts when you know there's really nothing you can do to help," said Herdt, 22, of Chesterfield, Burlington County.

So she went to Pennsylvania State University, majored in meteorology, and found a way to make a difference.

Using a National Science Foundation grant last summer, Herdt created a statistical model to better predict the ozone levels in the Philadelphia region, then spent her senior year tweaking her work. She, along with her mentors, is using it this summer at the Penn State Air Quality Forecast Office, which is responsible for issuing ozone alerts for the Philadelphia region, including Montgomery, Bucks, Delaware, and Chester Counties.

The good news is there haven't been that many bad ozone days so far: June 11, July 5, and Tuesday.

Wednesday, with its soaring temperatures, became the fourth.

"Mostly sunny skies, stagnant winds, and lingering pollutant buildup will keep ozone in the [orange alert] range," Herdt and her instructor, Amy Huff, wrote Tuesday on AirNow, a federal website where ozone levels are reported.

An orange alert means the air could be dangerous to vulnerable groups, specifically those with lung disease, the elderly, and youngsters.

Before 2013, most summers here saw 20 or more days where ozone reached Code Orange status, and other days when even higher warnings were issued and levels were dangerous to everyone. In 2007, there were 37 orange-alert days. Last summer, there were only six; the year before, five.

Both Herdt and Huff said it's too soon to say why ozone levels in the region have improved. Part of the reason, they surmised, can be attributed to more regulations on power plants, more environmentally friendly cars, and fewer heat waves.

Air quality alerts have been issued for years based on cloud cover, winds, temperatures - the hotter it is, the higher the risk - the current day's ozone level, and other factors.

But some of the older models were out of date because of changing environmental regulations that altered pollutants affecting the ozone.

"Some of the forecasting tools we had developed basically stopped working," said Huff, a member of the graduate faculty in the department of meteorology. "So [Herdt's work] is very significant. It helps us provide more accurate forecasts for the Philadelphia region."

This summer, Herdt is adjusting her model, which she said has been erring slightly on the high side in predicting ozone, in part because it doesn't account for thunderstorms, which can wash particles out of the air.

"It overpredicts a little bit," she said, but she has figured out by how much and accounts for that in issuing warnings.

She said she hopes other communities around the country will build similar models to make ozone prediction more reliable. Each metropolitan area has different geography, meteorological conditions, and other factors that mean the model has to be adjusted.

"What a lot of people don't understand is that air pollution is just as deadly as anything else," said Herdt, who worries not only about her cousin, but about her grandparents and her brother, who is healthy but practices soccer outdoors.

Herdt said her interest in air quality deepened during junior year, when she took a class co-taught by Huff and learned about the harmful effects of pollution. She cited, for example, hundreds of deaths in Chicago in 1995 during three days of high temperatures and poor air quality.

With more accurate warnings, those vulnerable can plan to stay in or limit vigorous outdoor activities, she explained.

Herdt spends about 30 minutes each day using her model to calculate ozone risk. Ozone forecasts are offered from May 1 to Sept. 30, the time when ozone peaks.

Herdt will leave next week to pursue a graduate degree in atmospheric science at Texas Tech University. Her model, however, will stay behind and continue to help those at the Penn State air quality office better predict ozone levels.

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