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

State and Local Information for EPA Region 1

Connecticut
Maine

Massachusetts
Rhode Island

Composite trend for available sites in these states:

EPA Region 01 (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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Connecticut

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

Abington, CT

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1998

2000

2002
Year

2004

2006


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Bridgetown, CT 8-hr Ozone Trends

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New Haven, CT 8-hr Ozone Trends

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1998 2000 2002

2004 2006

Year


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Maine

Ozone

On average, ozone adjusted for weather conditions declined 18 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

Ashland, ME

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Howland, ME

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1998 2000 2002 2004 2006

Year


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Massachusetts
Ozone

On average, ozone adjusted for weather conditions declined 8 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

Boston, MA 8-hr Ozone Trends

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Springfield, MA 8-hr Ozone Trends

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— Adjusted for Weather
	 Unadjusted for Weather

7998 2000 2002

Year

2004 200eT

Worcester, MA 8-hr Ozone Trends

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1998 2000 2002

2004 2006

Year


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Rhoda Island
Ozone

In Providence, RI, ozone adjusted for weather conditions declined 10 percent between
1997 and 2007. This improvement in ozone is in response to both state and regional
reductions in NOx and VOC emissions.

Trends for 1997-2007 for a site 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

Providence, RI 8-hr Ozone Trends

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