The summers of the 1990s produced alarming headlines in the local press (Knoxville News Sentinel). Headlines ranged from "Air Quality at Clingman's Dome hits Danger Level" to"Smoky's Air Quality Setting Worst Records". During the summer of 1998, air-monitoring stations in the Great Smoky Mountains National Park recorded the highest-ever eight-hour average ozone exposures. By late August, the National Park Service reported the 25th day of unhealthy ozone conditions for 1998. For the summer of 1999, the National Park Service reported the highest number of days (53) in the Great Smoky Mountain park which exceeded the new US EPA 8-hour ozone standard. The above split photograph was obtained from the U.S. EPA's WINHAZE system to illustrate the relative difference between "best" and "worst" days for the Great Smoky Mountains National Park (Tennessee's biggest tourist attraction).

While elevated ozone readings during the summers of the 1990s produced significant impact on the Great Smoky Mountains, the elevated readings within the nearby East Tennessee Valley have focused attention on potential economic and societal impacts of the new US EPA 8-hour ozone standard. For example, the News-Sentinel reported"Knox, 4 Neighbor Counties Won't Pass Ozone Tests: Chamber Official". The story suggested, "one way to reduce ozone levels would be to initiate a mass transit system and car pooling to take vehicles off the roads"; an option usually reserved for industrialized urban areas.

Because of the potential for significant impacts on the East Tennessee Valley from elevated ozone levels, the National Oceanic and Atmospheric Administration's Air Resource Laboratory's (NOAA/ARL) Atmospheric Turbulence and Diffusion Division (ATDD) in Oak Ridge, TN, initiated a measurement and prediction program with the specific goal of developing an air-quality forecasting system for East Tennessee. With the 2003 implementation of NOAA/EPA air quality air quality forecast initiative the regional network provides a verification/validation target for the predictive modeling system. Current partners in this effort include the National Weather Service, The University of Tennessee, National Park Service, and the State of Tennessee. Aside from supporting air quality forecasts, the data will also address key question is whether local measures and emissions restrictions will have the desired result of reducing local ozone concentrations, or whether changes must be enacted on a much broader scale to reach that goal.

Program

The ETOS program is designed as a multi-year effort. ETOS 1999-2002 served as scoping and feasibility studies during which new measurement techniques, an expanded micro-meteorological monitoring network, and various vertical atmospheric/chemical sounding systems were tested. ETOS 2003 developed a regional ozone database to include both mean hourly averages and hourly histograms of individual measurement readings. With the 2003 study, ETOS was accepted by NARSTO (Formerly an acronym for "North American Research Strategy for Tropospheric Ozone," the term NARSTO has become simply a wordmark signifying this tri-national, public-private partnership for dealing with multiple features of tropospheric pollution, including ozone and suspended particulate matter) for inclusion in the comprehensive ozone research database. The 2003 study period was intended to provide a demonstration and evaluation/validation database for the various operational and development air quality forecast model components ( http://www.nws.noaa.gov/ost/air_quality/ ). ETOS observation sites provide a regional view to supplement Tennessee's regulatory network (http://www.state.tn.us/environment/apc/ozone/ozonesitemap.php). The full scope of ETOS 2000+ is continuously under planning and review, and is refined each year using previous years analysis and experience to focus on particular issues within the East Tennessee region.

Background

ETOS builds on an ozone measurement program, SETOS, conducted by NOAA/ATDD and the University of Tennessee during the summer of 1995. As illustrated in Figure 1, nighttime vertical profiles of ozone within the East Tennessee Valley show high concentrations of ozone only a few hundred meters above the surface. This reservoir of ozone is trapped each evening above a surface-based inversion, which limits any potential mixing of ozone to the ground. About mid-morning, this reservoir of ozone is tapped by rising thermals generated by the rising sun, thus allowing quite high ozone concentrations to be mixed downward to the Earth's surface. The resulting high ground-level ozone concentrations are NOT fully attributable to local smog generation but are due largely to the morning "fumigation" phenomenon. Figure 1 also illustrates the particular difficulty faced by the National Park Service in the GSMNP (Great Smoky Mountain National Park). As explained by Dr. Wayne Davis of the University of Tennessee, during the night an elevated inversion level develops within the East Tennessee valley, forming an effective barrier preventing ozone transport to the surface. Since ozone reacts readily with most surfaces including vegetation, ground-level concentrations are rapidly reduced at night to normal background levels of 20-40 ppb (parts per billion). However, the ozone trapped above the inversion remains, and may be carried by the wind many miles from its point of formation without much dilution. For the Great Smoky Mountains, this means that higher elevations will not only experience the daytime maximum concentrations from local production, but will also experience high readings at night due to atmospheric transport. This is highlighted in the attached plots of ozone concentrations from the East Tennessee Valley monitoring sites as compared to Great Smoky Mountain sites. As shown in Figs. 2 and 3, ozone concentrations measured at the Freels Bend (FB) valley site near Oak Ridge exhibit a nighttime minimum as well as a daytime maximum; contrast this with the sample from Clingman's Dome, (CD), which shows a relatively flat time history. It seems likely that the ozone levels recorded in the Great Smoky Mountains cannot simply be attributed to local production, but the result of transport from other areas, perhaps from across the Southeast and Central United States.  

Goal

The goal of the ETOS program is to develop a high resolution/high fidelity meteorological and photochemical regional assessment for the East Tennessee Valley. It is not the goal of ETOS to conduct complete detailed chemical monitoring across the Valley, but rather to select ozone and fine particulates as its primary targets. While complete chemical monitoring (core sites) is conducted by the NPS within the GSMNP boundaries and by NOAA at the Walker Branch Watershed station, the ETOS framework is a regional picture of a few selected pollutants to define regional impacts and extend the knowledge base obtained at the core sites across the Valley region. This regional database will form the basis for assessing, predicting, and altering air quality levels. Observational goals are to ensure monitoring site adequately address the unique ridge/valley structure of the East Tennessee Valley. Towards these goals, the NOAA/ATDD RAMAN network has been instrumented with ozone monitors. Ozone monitors are located to examine within grid (typical chemistry and meteorological calculation grids are 12 km x 12 km) and grid-to-grid variability. In addition to the fifteen RAMAN sites and additional five-to-eight locations are also instrumented with both meteorological and ozone measurement systems. Combined, this network of monitoring stations provides a comprehensive regional measurement platform.