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Which Month Predominated for the Highest 8-Hour Daily Maximum Ozone Concentration for the Following Sites?


Ozone Quiz


Which Month Experienced the Highest 8-Hour Daily Maximum Ozone Concentration for the Following Sites?


Glacier National Park - May (2008), June (2009), and May (2010)
Yellowstone National Park - April (2008), Sept* (2009), and April (2010)
Denali National Park - April (2008), April (2009), and April (2010)
Trinidad Head - April (2008), April (2009), and March (2010)
*The US EPA notes in its database that September 2009 ozone readings were affected by a wildfire in Yellowstone National Park. The second highest 8-hour average ozone concentration at the site was in May.

The Springtime Months of April and May Predominated

The highest 8-hour daily maximum concentration occurred for most of the sites during the spring months. Lefohn et al. (2001) and Oltmans et al. (2008) discuss the variability of background ozone. The ozone monitoring site at Trinidad Head, CA is a site that many times meets the criteria for identifying surface ozone policy-relevant background levels. For more information about policy-relevant background, please click here. An Internet-based slide presentation is available for purposes of previewing the Lefohn et al. (2001) paper. For more information about background ozone and ozone trends, please visit our publication web page.


Lefohn A. S., Oltmans S. J. , Dann T. , and Singh H. B. (2001) Present-day variability of background ozone in the lower troposphere. J. Geophys. Res., 106 (D9):9945-9958.

Oltmans S. J., Lefohn A. S., Harris J. M., and Shadwick D. (2008) Background ozone levels of air entering the west coast of the U.S. and assessment of longer-term changes. Atmospheric Environment. 42:6020-6038.

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