The colored shading indicates the average relationship between the 8-hour mean surface ozone concentration and the strength of the El Nino events over the continental United States between 1980 and 2016. Orange colors indicate surface ozone concentrations increase, while blue colors indicate that they decrease, with strong El Nino events. The black dots indicate regions where the relationship is statistically robust. Credit: Shen and Mickley, 2017, Figure 2b
Source: Geophysical Research Letters

Ozone in the atmosphere near Earth’s surface is a key criteria pollutant, toxic to humans, other animals and vegetation. Surface ozone concentrations, regulated in the United States by the Environmental Protection Agency to not exceed a specific threshold in any given region, are affected by both atmospheric chemistry involving anthropogenic pollutants and atmospheric winds that mix, disperse, and transport ozone and its precursors from one location to another. Understanding the drivers of interannual variability in local and regional surface ozone concentrations is thus important for development and evaluation of effective regulatory policy. Shen and Mickley [2017] show that the El Niño Southern Oscillation (ENSO), a natural feature of sea surface temperature anomalies in the tropical Pacific that affects atmospheric circulation patterns, can explain some of the interannual variability in the levels of surface ozone throughout the eastern United States. Moreover, they also show that patterns of surface ozone changes due to El Niño can be predicted 4 months ahead of time using metrics that indicate the strength of an ongoing El Niño event.

Citation: Shen, L., & Mickley, L. J. [2017]. Effects of El Niño on summertime ozone air quality in the eastern United States. Geophysical Research Letters, 44, 12,543–12,550.

—Joel A. Thornton, Editor, Geophysical Research Letters

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