Tool can predict inversions long before pollution sets in

Want to know how likely an inversion is in the next month?

The USU-based Utah Climate Center has a new Inversion Forecast that's considered accurate out to 30 days — far longer than the state's three-day air-quality predictions, creating an opportunity to reduce driving or take other action that might temper or prevent pollution spikes associated with inversions.

Available on the Utah State University website at climate.usurf.usu.edu/inversion.php, the Inversion Forecast currently predicts inversions in the Salt Lake Valley later in January and in mid-February.

The forecast looks at fewer variables to focus on a single atmospheric phenomenon — the inversion, explained Robert Gillies, director of the Utah Climate Center.

The three-day air-quality forecasts take into account a larger dataset, making longer-term forecasting more difficult.

By taking a narrow approach to predicting inversions, this new forecasting model is able to predict long inversion events well into the future, he said.

Gillies said he and his team had initially taken note of the correlation between Utah's inversions and high pressure systems. That's a logical connection, given that high pressure systems are associated with calm weather, and calm weather is associated with inversions.

But the team had a breakthrough, Gillies said, a couple of years ago when it found a connection between high pressure systems in northern Utah and the Madden-Julian Oscillation in the Western Pacific.

The Madden-Julian Oscillation is a periodic tropical disturbance much like the better known El Nino, Gillie said. But unlike El Nino, the oscillation occurs more frequently, with a cycle that repeats every 30 to 60 days. Meteorologists can predict the Madden-Julian Oscillation with a fair degree of accuracy, he said, and that model gave his team the basis for their new method of forecasting inversions in northern Utah.

Over the past few years, he said, the Utah Climate Center has tested its model and compared it to how the actual weather panned out.

"Basically, we could go out 30 days and predict those inversion events with reasonable skill," Gillies said. "We did a number of comparisons, but the model did very well."

Gillies said the center is still in the process of refining the forecasts' visual presentation on the website.

Currently, the probability of an inversion on any particular day is represented by a blue bar graph. On days when the blue bars are taller than an horizontal orange line, an inversion event is likely.

Bo Call, manager of the Utah Division of Air Quality's Air Monitoring Center, has said it takes about four days of sustained inversion for harmful levels of air pollution to accumulate on the Wasatch Front.

Having this kind of advance notice is critical for sensitive populations whose health is significantly impacted by air pollution, Gillies said. For example, he said, some elderly residents are unable to go outside during prolonged inversions, lest the poor air quality trigger health conditions.

"If you can know two to three weeks out, you can plan," he said. "You can get your groceries in advance."

But others might appreciate the forecasts as well, he said, such as pregnant women who are concerned about exposing their unborn children to pollution, or athletes who would prefer to reschedule their training sessions to avoid the negative effects of polluted air.

Hospitals and doctors could plan for an influx of children and adults with respiratory conditions and plan accordingly. The environmentally conscious could arrange carpools to decrease emissions and avoid pollution buildup.

In the long term, Gillies said, that kind of action might even prevent the pollution from accumulating in the first place.

epenrod@sltrib

Twitter: @EmaPen