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A Pollution Episode Unveiled: A Detailed Study of NOx Emissions

Explore the dynamics of NOx emissions in a pollution episode, examining transport modes, sources, and effects on air quality following a severe weather pattern. Dive deep into pollutants' behaviors during a typical day, covering ozone levels, temperature inversions, and more.

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A Pollution Episode Unveiled: A Detailed Study of NOx Emissions

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  1. METO 637 Lesson 19

  2. NOx emission inventory

  3. VOC Emissions

  4. Sulfur Dioxide emissions

  5. A Typical Day in a Pollution Episode • A common severe pollution weather pattern occurs when high pressure is centered just west of the Mid Atlantic region. • Circulation around the high pressure center moves pollution from points west into the mid-Atlantic. H

  6. Fort Meade profile 6/19/2001

  7. After Sunrise Ozone Levels Increase Sharply • The ground heats up and the warm air above it erodes the inversion. • Ozone and other compounds above the inversion layer mix with the pollution under the layer. • This causes a dramatic increase in ground-level ozone, beginning around 10 AM. Sub. inv. Altitude  Noct. inv. Temperature

  8. Ozone Levels Reach a Maximum in the Afternoon Sub. inv. Sub. inv. Altitude Altitude  Noct. inv. Temperature Temperature

  9. After Sunset • If the weather remains the same, the temperature inversion forms again after dark. • Ozone concentrations above the inversion remain at a constant, relatively, high level. • Ozone trapped under the inversion reacts with other pollutants, and the surface; the ozone concentration diminishes. Altitude Ozone concentration remaining constant Temperature Inversion Ozone concentration diminishing Temperature

  10. Westerly transport is often present when the highest ozone is observed in the mid-Atlantic. 24 hr. Back-trajectories on days of 1-hr. ozone exceedances from 1997 through 2002, Baltimore area

  11. Aircraft measurements of ozone

  12. Aircraft measurements of Sulfur Dioxide

  13. Lee Side Trough Upper level winds from the west… …are turned by the lee side trough daytime

  14. Low Level Jet Air pollution from the southwest… …comes into Maryland overnight nighttime

  15. Plot of low-level winds from the Fort Meade, MD wind profiler during a high ozone episode LLJ LLJ LLJ

  16. Rapid Update Cycle (RUC) model depiction of the LLJduring a high ozone period (high wind speeds in red). 9:00 PM 11:00 PM 01:00 AM 03:00 AM 05:00 AM 07:00 AM

  17. Modes of Transport All three modes of transport are important when the highest pollution values are observed in the mid-Atlantic. • Large scale ~ 800 km (~70-100 ppbv) • (Much of the Eastern US) • Medium scale ~ 200- 800 km • (Carolinas to New England Region) • Small scale ~ 100 km • (N. Virginia to Baltimore, • Research Triangle to NC/VA border)

  18. Sources • Different types of transport imply different types of sources • Local transport Cars, industry, and other sources in the local area • Long distance transport Primarily power plants to W, though plumes from cities certainly contribute. • Low level jet Primarily cars and other low level sources; moves from SW to NE

  19. Effects of the August 15, 2003 Blackout on Air Quality Selinsgrove, PA Compared with Aug 4, 2002 Coming soon to GRL

  20. Effects of the 2003 Blackout on Air Quality CEM data indicate reductions of 60-80% L. Marufu, B. Taubman, B. Doddridge et al.

  21. Effects of the 2003 Blackout on Air Quality

  22. In summary • It isn’t all transport… • It isn’t all local… • It isn’t all power plants… • It isn’t all automobiles… • The problem will not be solved by addressing any one of these problems individually. ALL of these will have to show significant reductions for us to breathe clean air.

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