In order to understand how weather and ozone are related we first must understand how exactly ozone forms. There are a few key ingredients to the formation of tropospheric ozone: volatile organic compounds (VOC), sunlight, and warmth. VOCs are generated through emissions anywhere from industrial facilities to the tailpipe of people’s cars. These compounds are spewed into the air on a daily basis but in high concentrations can cause issues. In areas of high concentrations, and with the help of sunlight, a chemical reaction occurs that creates tropospheric ozone or ground-level ozone which is what it is sometimes called. We are all aware of ozone higher up in the atmosphere, called stratospheric ozone, that actually protects us from harmful UV rays. However, ground-level ozone, is actually harmful to humans and plants.
Now, where does weather come in? As we all know, weather influences our day-to-day lives whether that is with rain, sunshine or overcast skies. Weather influences the “life-cycle” of ozone as well. Wind patterns can carry ozone plumes across countless miles which affects areas that could be hundreds of miles away from where the initial source is. A perfect example of this is the Great Lakes. Chicago, being a populated area with industrial facilities within its reach produces the ozone precursors (VOCs) and when winds are southwesterly in the region, those VOCs travel across Lake Michigan and can impact areas within the southwest Michigan region. A prime day for ground-level ozone production in that region is southwest winds, clear skies, and a hot day. If the air temperature is too cold, ground-level ozone tends to not produce as much as it does on a hot day. Also, if there isn’t ample sunlight, like on an overcast day, ozone production is cut-off because it needs sunlight in order to produce the chemical reaction needed in order to form.
This is why ground-level ozone can be variable as it is very dependent upon the overall weather it occurs in. Forecasting weather patterns helps immensely when it comes to forecasting overall air quality, because the weather can tell you if there will be any ground-level ozone plumes forming or approaching from another area upwind from your location.
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©2022 Meteorologist Alec Kownacki