Ground level ozone is formed by a chemical reaction between volatile organic compounds (VOCs), also known as hydrocarbons and oxides of nitrogen (NOx) in the presence of sunlight. Nitrogen oxides and hydrocarbons are known as the chief "precursors" of ozone. These compounds react in the presence of sunlight to produce ozone. These gaseous compounds mix like a thin soup in the atmosphere, and when they interact with sunlight, ozone is formed. Due to the nature of this reaction, ozone concentrations can reach unhealthful levels when the weather is hot and sunny with little or no wind. As a result, ground level ozone pollution, or smog, is mainly a daytime problem during summer months.

The photochemical reaction, described above, that produces ground level ozone requires several factors to be present and tends to occur when a stagnant air mass develops during hot and sunny conditions. The air will not become stagnant if weather systems continue to move through the area and displace the air with cleaner, "fresher" air.

One day alone is usually not enough to form excessive ozone. Usually it takes several days in a row, with the hot temperatures, the wind speed low, and the sky sunny for an ozone event to occur. Therefore tracking weather conditions are an integral part of tracking ozone.

But is it possible to predict ground level ozone? In this lesson, students will access near real-time ozone data and weather data to predict if there will be ground level ozone in their area tomorrow.
 

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