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

State and Local Information for EPA Region 8

Colorado
Utah

Wyoming

Composite trend for available sites in these states:

EPA Region 08 (selected sites)

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	 Adjusted for Weather

 Unadjusted for Weather

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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Colorado
Ozone

On average, ozone increased 6 percent between 1997 and 2006. Ozone trends vary 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

Rocky Mtn NP, CO

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CL
CL

Adjusted for Weather
Unadjusted for Weather

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60-

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CO
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CD
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1998 2000 2002 2004 2006
Year


-------
Denver, CO

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- 40

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	 Adjusted for Weather

 Unadjusted for Weather

1998

2000

2002
Year

2004

2006

Gothic, CO

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CO

2

CD

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Adjusted for Weather
Unadjusted for Weather

1998

2000

2002
Year

2004

2006


-------
Mesa Verde NP, CO

.Q
CL
Q.

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c

o

N

O

,60

O)

CO

CD

- 40

CO
c
o

CO
CO

CD 20
|C/)

Adjusted for Weather
Unadjusted for Weather

;8.0;

1998

2000

2002
Year

2004

2006


-------
Utah
Ozone

On average, ozone increased 5 percent between 1997 and 2006. Ozone trends vary 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

Salt Lake, UT



	 Adjusted for Weather

 Unadjusted for Weather

	1	1	1	1	1

1998 2000 2002 2004 2006
Year

.Q
CL
Q.

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N

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CO

2

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CO

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Canyonlands NP, UT

.Q
CL
Q.

CD 80

c

o

N

O

,60

O)

CO

CD

- 40

CO
c
o

CO
CO

CD 20
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Adjusted for Weather
Unadjusted for Weather

1998

2000

2002
Year

2004

2006


-------
Wyoming
Ozone

On average, ozone declined 1 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

Pinedale, WY

.Q
CL
CL

Adjusted for Weather
Unadjusted for Weather

cd 80 -

c
o

N

O

CD
>

CO
c
o

c/)

1998 2000 2002 2004 2006
Year


-------
Centennial, WY

.Q
CL
Q.

CD 80

c

o

N

O

,60

O)

CO

CD

- 40

CO
c
o

CO
CO

CD 20

an

Adjusted for Weather
Unadjusted for Weather

.l.i  l;

1998

2000

2002
Year

2004

2006


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