Observed Relationship between Ozone and Temperature for Urban Nonattainment Areas in the United States

This study examined the observed relationship between ozone (O-3) and temperature using data from 1995 to 2020 at 20 cities across the United States (U.S.) that exceed the O-3 National Ambient Air Quality Standard (NAAQS). The median slope of the O-3 versus temperature relationship decreased from 2.8 to 1.5 parts per billion per degrees Celsius (ppb & DEG;C-1) in the eastern U.S., 2.2 to 1.3 ppb & DEG;C-1 in the midwestern U.S., and 1.7 to 1.1 ppb & DEG;C-1 in the western U.S. O-3 in the eastern and midwestern U.S. has become less correlated with temperature due to emission controls. In the western U.S., O-3 concentrations have declined more slowly and the correlation between O-3 and temperature has changed negligibly due to the effects of high background O-3 and wildfire smoke. This implies that meeting the O-3 NAAQS in the western U.S. will be more challenging compared with other parts of the country.

Automated summary

This study analyzed the relationship between ozone (O-3) and temperature in 20 cities across the United States from 1995 to 2020. The study found that the correlation between O-3 and temperature has decreased in the eastern and midwestern U.S. due to emission controls, while in the western U.S., O-3 concentrations have declined more slowly because of high background O-3 and wildfire smoke. This suggests that meeting the O-3 National Ambient Air Quality Standard in the western U.S. will be more challenging compared to other regions.