It's ozone season

Ozone season in the Kansas City region started March 1 and runs through Oct. 31. After the 2023 ozone season started early with the first Ozone Alert Day in May, what can we expect for this year?

Sullivan Brown, Weather or Not operations manager, shared his outlook for the year at a recent MARC Air Quality Forum. He said a study of the 2010 and 2020 seasons, which are similar to this year, look more normal and neutral.

The oxygen that we breathe normally is a stable molecule with two oxygen atoms called a diatom. However, there’s an unstable molecule with three oxygen atoms: ozone. Ozone molecules search for surrounding molecules that they can react with to give up the extra oxygen atom so it can return to a stable diatom. This makes ozone an oxidizer – kind of like hydrogen peroxide in gaseous form. 

“Good ozone” is naturally present in the stratosphere (as the ozone layer) between 9-18 miles above us where energy from UVB radiation is absorbed to constantly break apart and reform these oxygen atoms from the two types of molecules. This process reduces the radiation responsible for skin aging and cancer risk at the earth’s surface.  Then there is “bad ozone;” human-made ozone that forms when sunlight reaching ground level causes a chemical reaction between several gases in smog. Inhaled ozone is a hazard to public health because it can trigger breathing problems, especially in those who have asthma, emphysema or other respiratory conditions.
 

Above-average temperatures and below-average humidity contribute to ozone formation, said Doug Norsby, MARC air quality senior planner. Scientists compare past years with the current weather conditions when forecasting. According to the U.S. Environmental Protection Agency, variations in weather conditions play an important role in determining ozone concentrations, but weather forecasts are typically only accurate three to 10 days in the future. So, Brown and his organization track such things as changing ocean temperatures and long-term drought conditions when considering an outlook for ozone season. 

“Oceans give the first hints,” Brown said. “We had an El Niño winter (ocean surface warming) this year. So, we were seeing a lot of mild water along the equator. While it still looks very mild currently down there, it is starting to cool and has been cool here for the last few months. The projection going forward is to trend toward a more neutral summer to eventually an El Niño winter on the back end of things.” 

The ocean currents offer an indication for where prevailing high- and low-pressure areas will form and how strong they will be as well as the likelihood for above- or below-average temperatures and precipitation.

The two years that serve as a model for this year’s forecast are 2010 and 2020. Brown said there were a fair amount of early season exceedances in 2010, which had the most exceedances in June and August and a fair amount of yellow conditions. Brown said that 2020, another model year and a pandemic year, saw a loss of travel, which helped keep air pollution down.

“That year was very clean overall,” Brown said. “Yellow days peaked in June, July and August. Looking at the weather patterns, it seems like we’re probably on that same track for this year of peaking in June, July and August, which isn’t uncommon anyway, given those are the peak heating months of the year as well.”

Brown said that as the ozone season progresses, things will swing back and forth and average up.

“There will be times when it’s milder, times when it’s cooler, but on average overall. It’s going to end up more seasonal … from a temperature perspective, which is probably good news from the ozone production front.”

Brown said that soaking rainfall events in April and May will also help keep down ozone levels.

“As we go forward into June, July and August, the pattern really starts to flip,” Brown said. During those three months, Brown said we would experience more of the milder patterns that can be set up in the central and eastern U.S. 

From the precipitation side of things, Brown said the Kansas City region is looking at more of a pattern that is conducive for active, above-normal precipitation, especially in June. 

“Will there be times when we are drier and have more potential for exceedances? Yes,” Brown said. “But it’s not going to be like a 2012 situation where it’s bone dry and hot every day and we’re doing the exceedance thing every day or every other day. We’ll still see precipitation during the summer. The drier locations will be more into the northeast. This will help with our drought situation.”

As the ozone season ends, Brown said we will see a cooler pattern to wrap up September and October. He said there’s always a possibility for things to change.

“But that’s something we’ll have to deal with as we get closer.”