Weather Makes a Difference: 8-hour
Ozone Trends for 1997-2006

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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	 Adjusted for Weather

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1998

2000

2002
Year

2004

2006

U.S. Environmental Protection Agency

Office of Air and Radiation

Office of Air Quality Planning and Standards

April 2007


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Illinois

Ozone

In Chicago ozone declined 10 percent between 1997 and 2006. 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 1997-2006 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 more 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

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	 Adjusted for Weather

— Unadjusted for Weather

1998

2000

2002
Year

2004

2006


-------
Indiana

Ozone

On average, ozone declined 12 percent between 1997 and 2006. 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 1997-2006 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 more 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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1998 2000 2002 2004 2006
Year


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Fort Wayne, IN

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— Unadjusted for Weather

1998

2000

2002
Year

2004

2006

Indianapolis, IN

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— Unadjusted for Weather

1998

2000

2002
Year

2004

2006


-------
Salamonie Reservoir, IN

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1998

2000

2002
Year

2004

2006


-------
Michigan
Ozone

On average, ozone declined 10 percent between 1997 and 2006. 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 1997-2006 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 more 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

Unionville, Ml

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1998

2000

2002
Year

2004

2006


-------
Ann Arbor, Ml

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1998

2000

2002
Year

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2006

Detroit, Ml

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1998

2000

2002
Year

2004

2006


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Grand Rapids, Ml

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— Unadjusted for Weather

1998

2000

2002
Year

2004

2006


-------
Minnesota
Ozone

On average, ozone declined 4 percent between 1997 and 2006. 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 1997-2006 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 more 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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1998 2000 2002 2004 2006
Year


-------
Minneapolis, MN

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1998

2000

2002
Year

2004

2006


-------
Ohio

Ozone

On average, ozone declined 9 percent between 1997 and 2006. 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 1997-2006 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 more 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

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1998

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2002
Year

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2006


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Akron, OH

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Cincinnati, OH

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1998

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Year

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Cleveland, OH

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Columbus,OH

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Dayton, OH

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1998

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Deer Creek, OH

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1998

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Year

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Lykens, OH

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1998

2000

2002
Year

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2006

Oxford, OH

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1998

2000

2002
Year

2004

2006


-------
Toledo, OH

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— Unadjusted for Weather

1998

2000

2002
Year

2004

2006


-------
Wisconsin
Ozone

On average, ozone declined 11 percent between 1997 and 2006. 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 1997-2006 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 more 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

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Q.

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— Unadjusted for Weather

1998

2000

2002
Year

2004

2006


-------
Madison, Wl

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— Unadjusted for Weather

1998

2000

2002
Year

2004

2006


-------