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) ^ 80 CL O70 c n 60 O 0 cn CO 50 CO CD > 40 < ro c o CO $ 20 if) 30- 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 ------- 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 .Q CL CL Adjusted for Weather Unadjusted for Weather cd 80 - c o N O £60- CD CO CO %' CD > CO c o c/) 1998 2000 2002 2004 2006 Year ------- Denver, CO .Q CL Q. CD 80 c o N O £,60 O) CO CD - 40 CO c o CO CO CD 20 an .o -^8 "o~ Adjusted for Weather — Unadjusted for Weather 1998 2000 2002 Year 2004 2006 Gothic, CO .Q CL Q. CD 80 c o N O £,60 CO 2 CD ^ 40 CO c o c/) CO .s20 Adjusted for Weather Unadjusted for Weather 1998 2000 2002 Year 2004 2006 ------- Mesa Verde NP, CO .Q CL Q. CD 80 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. cd 80 - c o N D £,60 H CO 2 CD ^ 40 H CO c o c/) CO $ ------- Canyonlands NP, UT .Q CL Q. CD 80 c o N O £,60 O) CO CD - 40 CO c o CO CO CD 20 |C/) 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 ------- |