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Investigating Surface Ozone Dynamics in the Southeastern United States During Fall

This study explores the characteristics and variability of surface ozone in the Southeastern United States during the fall months of September and October. Employing a 3D chemical transport model, we analyze trends, inter-annual variability, and the influencing meteorological and emission factors on ozone levels. Our findings indicate a notable sensitivity to biogenic emissions compared to NOx reduction and reveal fluctuations in ozone levels over recent decades. The study emphasizes the implications of climate change on fall ozone and provides simulations for better understanding and management of air quality.

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Investigating Surface Ozone Dynamics in the Southeastern United States During Fall

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  1.  EAS 6792 Surface Ozone during Fall in the Southeastern United States Yuzhong Zhang April 23, 2013

  2. Why cares about ozone during fall? Sept., Oct. June, Aug. Nolte et al., 2008 Chen et al., 2009

  3. What interests us? • Southeast US • October What are the features of monitoring data in October? Mean, Trend, Variability， Distribution • Features • Factors • Simulation • Sensitivity What factors affect the October ozone in SE US? Meteorology, Emission Is a current 3D chemical transport model able to simulate October ozone? Day-to-day, Inter-annual Is the sensitivity of ground ozone in October different from that in summer months? Implications? ?

  4. Features Distribution MDA8

  5. Features Variance Var(all) = Var(Spatial) + Var(Inter-annual) + Var(Day-to-day)

  6. Trend, variability, and extremes Features 0.11±0.16 ppbv/yr 2σ

  7. IAV of O3 and meteorology Factors Inter-annual variability of ozone R = -0.80 R = -0.13 Ozone ppbv Oct. 2010

  8. MDA8 O3 in Oct. 2010 and met. Factors Day-to-day variability of ozone R = 0.71 R = -0.58 Ozone ppbv

  9. Modeled monthly mean Simulation Regional chEmicaltrAnsport Model (REAM) Oct., 2010 Monthly mean afternoon ozone Observation Model

  10. Simulation Modeled day-to-day variation

  11. Comparison with summer Sensitivity Oct. ozone has • Less effectiveness of NOx emission reduction • Stronger sensitivity to biogenic emission

  12. Conclusions • No significant trend in last three decades • Increased inter-annual variability • Extremely high ozone year of 2000 and 2010 • Correlation between cloud fraction and monthly mean October ozone. Records show

  13. Conclusions Model simulation shows • Capability to reproduce monthly mean • Less day-to-day variability than observations Model sensitivity analysis shows • Less benefit from NOx emission reduction • Greater impact of biogenic emission Climate change may play a bigger role in fall than in summer

  14. Supplemental slides

  15. Supplemental slides ΔO3 due to 20% reduction of NOx emission Fall Summer

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