1. WESTAR Technical Committee Ozone Workgroup May 2005
Ozone in the West
Ozone transport in the Eastern U.S. is a well documented phenomenon. However, in the West, only a handful of studies have examined ozone transport on a regional scale. These studies have been limited in scope, usually focusing on a specific city, episode or rural area feature such as National Parks. Due to the widespread nature of ozone non-attainment areas in the East, much greater attention has been paid to monitoring and modeling studies confirming the buildup and transport of ozone precursors or ozone rich air masses over large distances. Exceedances of the 8-hour standard in the Northeast have been tracked back to contributions of pollutants from areas as far west as Texas. Yet, in the West, ozone has been traditionally thought of as an isolated problem, unique to a limited number of high density population areas. The WESTAR Ozone workgroup spent the past year looking at issues related to elevated ozone concentrations in the West to determine if high levels of ozone can be caused by local emissions or transport of ozone rich air masses. Current evidence suggests some ozone problems may be due to transport, global background or emissions from natural, or manmade fires. In such cases, local controls may be largely ineffective in reducing local ozone.
WESTAR Technical Committee Ozone Workgroup
May 2005

2. Ozone Workgroup Goals
1.Provide states with scientifically sound data and analyses to support ozone SIPs, especially for areas where transport may be a significant contribution to local and regional concentrations.
2. Monitor national decisions on ozone that may affect the west
At the fall business meeting, the Ozone Workgroup presented a Phase I report documenting many of the ozone transport studies in the Western and Eastern U.S. Several situations in the West, such as modeling work for SIPs, Asian transport studies and natural events exclusions were documented. These all have potential SIP impacts for other Western states. Denver modeling showed high levels of ozone being transported into the area during some of the worst case events in 2002, adding 50% to 70% of the total ozone burden during episodes. Utah documented substantial impacts on ozone in Salt Lake City due to emissions from upwind fires. Other fire episodes in Mexico have been shown to significantly impact ozone levels to the point of causing violations of the NAAQS. Studies in Arizona showed incidents of ozone and precursor rich air entering the area from southern California on days when ozone exceeded federal standards. Studies of Asian transport of pollutants indicated increasing background ozone levels over the past 15 years and possible contributions to high ozone events on the West coast in some cases. Development in the west has lead to the large scale hydrocarbon and NOx sources in many rural Western areas. Analysis of trends in ozone in the West showed many locations where ozone concentrations are increasing over the past ten years.
Considering ozone issues in the West in a broader context and anticipating how national controls may help or hinder ozone in the West is part of the charge of the workgroup.

3. 8-hour ozone nonattainment areas
While most ozone non-attainment areas are in California, Arizona, New Mexico, Colorado and other western states all have ozone challenges. Denver and Farmington (NM) completed EAC plans for ozone; other areas of the west may be required to complete ozone SIPs in the future.

4. Ozone Trends at National Parks
This graphic from the NPS shows ozone trends in National Parks. Note that in many western national parks, ozone is increasing significantly (red arrows) from
While ozone trends in National Parks (somewhat of a measure of ‘rural ozone’) is decreasing in many areas of the West where major precursor control programs are in place, numerous Western States are monitoring increased ozone concentrations over the past ten years. The success of California’s attack on ozone is evident in the graphic but in the reaches outside of the direct control area, downwind of the West Coast, you can see discouraging trends of ozone most other areas.
The non-urban nature of most of these monitoring sites indicates the extent of the ozone problems reaching past the traditional urban boundary into remote regions. While some areas like Rocky Mountain National Park can be heavily influenced by localized Denver area ozone production, other areas are much more remote.

5. What is causing high ozone concentrations?
EACs for Denver, Four Corners indicate very little contribution from local sources
Transport
Global background
Impacts of fire
Growth in the west
Sources related to oil and gas development in many Western States are increasing at a substantial rate and growth projections through 2020 show significant adverse impacts due to emissions from these sources of Nox and hydrocarbons on rural visibility. Those same types of emissions are the key players in causing ozone formation. Projections of emission growth under proposed Federal programs do not indicate declining trends in the West like those anticipated in the East. Fires, shown to impact ozone production far downwind of the source may increase in the future as prescribed burning and drought continue to be factors to contend with.

6. Worldwide NOx Emissions Trends
Due to increases in Asian emissions, ozone in air arriving at the west coast of the US (transported from Asia across the Pacific) has increased by approximately 10 ppbv, this is approximately a 30% increase from the mid 1980’s to the present (Jaffe et al., 2003). Studies from Hirsch et al. 1996; Altshiller and Lefohn 1996; and Logan 1989 showed an increase in background concentrations of ppbv of O3 and NOy was recorded on the coast of the Western United States, most of which being transported from eastern Asian countries.

7. Long Range Transport of Smoke Emissions
Numerous examples from satellite data show the transport of smoke over long distances. This particular example shows that dispersion is not necessarily a big player in reducing atmospheric concentrations over long distances. Animated views of the Arizona fires show large smoke plumes impacting downwind areas hundreds of miles away. This smoke is rich in nitrogen oxides and hydrocarbons, primary components of making ozone. Fires in the West and Mexico have been shown to cause high ozone levels far downwind of the fire.

8. Another example of forest fires increasing levels of ozone in an area is the one week episode of increased ozone in Northern Utah, where concentrations for the entire monitoring network for ozone were elevated between July 28-August 3, Unusually high levels of visible smoke and haze in the area also accompanied this episode (Utah Division of Air Quality, 2001). This, along with monitoring data from previous years showing improvements in the 1-hour ozone levels helped provide proof that fires had a significant impact in increased levels of ozone during this event (Delaney, 2004).

9. Workgroup Accomplishments
Literature review and compilation
Western ozone episodes identified
Simple analysis of data to identify episodes where transport may be significant
Statistical approach developed to analyze western episodes
Other sources of tools for analysis identified
An analysis of ozone data in the West was the major focus of the work this year. The Phase I report, documenting transport issues in the West and the East was edited and a Web version was recently developed for the general public. This has been added to the Colorado Home Page and access will be made available through the WESTAR Web site. Each WESTAR state identified the top 20 (or more) ozone episodes over the past 6 years and this information was collected in a series of spreadsheets. A scan of the data was performed to establish if common ozone periods were observed on a regional basis. Several periods of interest were identified that warrant further examination. Graphic displays of high ozone events were generated and preliminary text for the Phase II report was drafted.
The complications of analyzing mass amounts of ozone data over a six year period made it clear that other analysis options need to be explored. A statistical analysis scheme was developed for the group as one of the more comprehensive tools to be used for future exploration of high ozone events. A second approach was suggested using a simpler, meteorological type cast type of method. In either case, more analysis of high ozone events in the West is warranted using more advanced tools to present a convincing argument that transport of precursors or high ozone background levels is an issue to be reckoned with in the West.

10. Data Analysis Challenge
An analysis of six years data for selected Western ozone monitoring sites was performed to look for signatures of regional events. Several periods of interest were identified where there appears to be a high ozone episode on the West Coast followed by elevated ozone in downwind States. Further examination of these events need to be made to determine how significant such events are. Here you see one of the periods of interest in Several upwind events precede the peak signatures in New Mexico and Colorado.

11. Future Work
Further analysis of identified episodes to determine whether transport is a factor (currently seeking $$)
Determine influence of Asian transport on western ozone concentrations
Determine contributions from fire events
Modeling analyses (with EPA support)
Decisions on the magnitude and direction of national controls focus attention on solving Eastern ozoneproblems but the West is largely ignored due to a lack of studies and data focusing on the issue of transport and regional scale ozone events.
Asian transported ozone appears to be increasing. Exceedances of the standards may be in part due to transported ozone, and as such, would make it difficult to control.
Fires have been documented to impact ozone in a negative or positive manner depending on proximity and meteorology. A process to track and document such impacts will be important for determining how to account for such events will be critical.