Weather Makes a Difference: 8-hour
Ozone Trends for 1997-2007

State and Local Information for EPA Region 5

Illinois

Indiana

Michigan

Minnesota

Ohio

Wisconsin

Composite trend for available sites in these states:

EPA Region 05 (selected sites)

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Year

2004

2006

U.S. Environmental Protection Agency

Office of Air and Radiation

Office of Air Quality Planning and Standards

April 2008


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Illinois

Ozone

In Chicago ozone adjusted for weather conditions declined 7 percent between 1997 and
2007. These improvements in ozone are in response to both state and regional reductions
in NOx and VOC emissions. The level of ozone improvement varies from site to site.

Trends for 1997-2007 for rural sites and urban areas with complete ozone and
meteorology data are presented below. Ozone season (May 1 - September 30) averages
of daily maximum 8-hour ozone were adjusted to remove the influence of year-to-year
variability in weather conditions. The dotted line shows the trend in observed values at
monitoring sites, while the solid line illustrates the underlying ozone trend after removing
the effects of weather. The solid line serves as a m ore accurate ozone trend for assessing
changes in emissions. Typical weather conditions are determined by averaging
conditions (e.g., temperature, humidity, etc.) for the time period presented. The
information provided is useful for reviewing the weather influence for a particular ozone
season. The solid line represents ozone levels anticipated under typical weather
conditions.

Seasonal Average 8-hour Ozone Trends

Chicago, IL 8-hr Ozone Trends

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Indiana

Ozone

On average, ozone adjusted for weather conditions declined 14 percent between 1997 and
2007. These improvements in ozone are in response to both state and regional reductions
in NOx and VOC emissions. The level of ozone improvement varies from site to site.

Trends for 1997-2007 for rural sites and urban areas with complete ozone and
meteorology data are presented below. Ozone season (May 1 - September 30) averages
of daily maximum 8-hour ozone were adjusted to remove the influence of year-to-year
variability in weather conditions. The dotted line shows the trend in observed values at
monitoring sites, while the solid line illustrates the underlying ozone trend after removing
the effects of weather. The solid line serves as a m ore accurate ozone trend for assessing
changes in emissions. Typical weather conditions are determined by averaging
conditions (e.g., temperature, humidity, etc.) for the time period presented. The
information provided is useful for reviewing the weather influence for a particular ozone
season. The solid line represents ozone levels anticipated under typical weather
conditions.

Seasonal Average 8-hour Ozone Trends

Vincennes, IN

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Fort Wayne, IN 8-hr Ozone Trends

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Salamonie Reservoir, IN

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Michigan

Ozone

On average, ozone adjusted for weather conditions declined 12 percent between 1997 and
2007. These improvements in ozone are in response to both state and regional reductions
in NOx and VOC emissions. The level of ozone improvement varies from site to site.

Trends for 1997-2007 for rural sites and urban areas with complete ozone and
meteorology data are presented below. Ozone season (May 1 - September 30) averages
of daily maximum 8-hour ozone were adjusted to remove the influence of year-to-year
variability in weather conditions. The dotted line shows the trend in observed values at
monitoring sites, while the solid line illustrates the underlying ozone trend after removing
the effects of weather. The solid line serves as a m ore accurate ozone trend for assessing
changes in emissions. Typical weather conditions are determined by averaging
conditions (e.g., temperature, humidity, etc.) for the time period presented. The
information provided is useful for reviewing the weather influence for a particular ozone
season. The solid line represents ozone levels anticipated under typical weather
conditions.

Seasonal Average 8-hour Ozone Trends

Ann Arbor, Ml

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Detroit, Ml 8-hr Ozone Trends

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Grand Rapids, Ml 8-hr Ozone Trends

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Unionville, Ml

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Minnesota
Ozone

On average, ozone adjusted for weather conditions declined 11 percent between 1997 and
2007. These improvements in ozone are in response to both state and regional reductions
in NOx and VOC emissions. The level of ozone improvement varies from site to site.

Trends for 1997-2007 for rural sites and urban areas with complete ozone and
meteorology data are presented below. Ozone season (May 1 - September 30) averages
of daily maximum 8-hour ozone were adjusted to remove the influence of year-to-year
variability in weather conditions. The dotted line shows the trend in observed values at
monitoring sites, while the solid line illustrates the underlying ozone trend after removing
the effects of weather. The solid line serves as a m ore accurate ozone trend for assessing
changes in emissions. Typical weather conditions are determined by averaging
conditions (e.g., temperature, humidity, etc.) for the time period presented. The
information provided is useful for reviewing the weather influence for a particular ozone
season. The solid line represents ozone levels anticipated under typical weather
conditions.

Seasonal Average 8-hour Ozone Trends

Voyageurs NP, MN

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Minneapolis, MN 8-hr Ozone Trends

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2002
Year

2004

2006


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Ohio

Ozone

On average, ozone adjusted for weather conditions declined 15 percent between 1997 and
2007. These improvements in ozone are in response to both state and regional reductions
in NOx and VOC emissions. The level of ozone improvement varies from site to site.

Trends for 1997-2007 for rural sites and urban areas with complete ozone and
meteorology data are presented below. Ozone season (May 1 - September 30) averages
of daily maximum 8-hour ozone were adjusted to remove the influence of year-to-year
variability in weather conditions. The dotted line shows the trend in observed values at
monitoring sites, while the solid line illustrates the underlying ozone trend after removing
the effects of weather. The solid line serves as a m ore accurate ozone trend for assessing
changes in emissions. Typical weather conditions are determined by averaging
conditions (e.g., temperature, humidity, etc.) for the time period presented. The
information provided is useful for reviewing the weather influence for a particular ozone
season. The solid line represents ozone levels anticipated under typical weather
conditions.

Seasonal Average 8-hour Ozone Trends

Youngstown, OH 8-hr Ozone Trends

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Akron, OH 8-hr Ozone Trends

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Cleveland, OH 8-hr Ozone Trends

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Columbus,OH 8-hr Ozone Trends

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Dayton, OH 8-hr Ozone Trends

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Lykens, OH

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Oxford, OH

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Toledo, OH 8-hr Ozone I rends

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Wisconsin
Ozone

On average, ozone adjusted for weather conditions declined 13 percent between 1997 and
2007. These improvements in ozone are in response to both state and regional reductions
in NOx and VOC emissions. The level of ozone improvement varies from site to site.

Trends for 1997-2007 for rural sites and urban areas with complete ozone and
meteorology data are presented below. Ozone season (May 1 - September 30) averages
of daily maximum 8-hour ozone were adjusted to remove the influence of year-to-year
variability in weather conditions. The dotted line shows the trend in observed values at
monitoring sites, while the solid line illustrates the underlying ozone trend after removing
the effects of weather. The solid line serves as a m ore accurate ozone trend for assessing
changes in emissions. Typical weather conditions are determined by averaging
conditions (e.g., temperature, humidity, etc.) for the time period presented. The
information provided is useful for reviewing the weather influence for a particular ozone
season. The solid line represents ozone levels anticipated under typical weather
conditions.

Seasonal Average 8-hour Ozone Trends

Milwaukee, Wl 8-hr Ozone Trends

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1998 2000 2002

2004 2006

Year


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Madison, WI 8-hr Ozone Trends

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