Ozone Modeling

Modeling Air Quality across Piedmont North Carolina

Walter Martin, Department of Geography and Earth Sciences, UNC Charlotte
Paul Smith, Center for Applied GIS, UNC Charlotte
Elie Saliba, College of Arts and Sciences, UNC Charlotte

Mobile emissions contribute precursors that can elevate the concentration of ground level ozone. Emission control strategies within Mecklenburg County are compared to provide decision support for air quality planning initiatives. Grid cell emission estimates for 2007 are integrated vertically and horizontally as the precursors for oxidants like ozone are transported downwind. Meteorological conditions taken from a 1997 episode favorable for ground level ozone formation are used to simulate a hypothetical episode in 2007. Atmospheric chemistry is modeled within each 4 km grid cell for each hour during the five day episode. In this analysis all “on-road” emissions of nitrogen oxides within Mecklenburg County have been reduced by 8.8 percent to simulate the effect of a potential emission control strategy on ambient ozone levels.

 

click on the image to see the animation (Quick Time .mov file)

In this animation changes in the ground level concentration of ozone are compared with a control simulation without any reduction of emissions. This level of emission reduction only results in a modest one part per billion (ppbv) reduction in ozone. The EPA 8 hr. standard for ozone is less than or equal to 80 ppbv. Warm colors show those areas where ozone is reduced and cool colors show areas where ozone is increased compared with the control. Notice these limited reductions in nitrogen oxide emissions reduced ozone concentration during the day when those levels spike in response to insolation, and conversely are increased during the night hours when ozone levels are naturally low. Hours are GMT.