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Comparing PM2.5 Simulations Over Eastern US: CB-IV vs. RADM2 Mechanisms

This study assesses CMAQ in simulating PM using CB-IV and RADM2 mechanisms, comparing with TEOM measurements, SEARCH and IMPROVE data, and emission reduction scenarios. Results show overprediction in TEOM measurements by both mechanisms, with RADM2 predicting higher PM2.5 concentrations. CB-IV simulations exhibit lower sulfate and higher nitrate levels compared to RADM2. RADM2 shows greater sensitivity to emission reductions than CB-IV.

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Comparing PM2.5 Simulations Over Eastern US: CB-IV vs. RADM2 Mechanisms

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  1. A comparison of PM 2.5 simulations over the Eastern United States using CB-IV and RADM2 chemical mechanisms Michael Ku, Kevin Civerolo, and Gopal Sistla New York State Department of Environmental Conservation Albany, NY

  2. INTRODUCTION • Assess CMAQ in simulating PM for two chemical mechanisms • Comparison with hourly TEOM (PM 2.5) measurements • Comparison with daily averaged PM2.5 and species data from SEARCH and IMPROVE (MANE-VU) • Sensitivity of the chemical mechanism to emission reductions

  3. MODEL SIMULATIONS • CMAQ (version 4.1) with CB-IV and RADM2 at 36km and 16 vertical layers • MM5 run at 108/36/12 km nesting grids and 25 vertical layers up to about 16 km • 1995 EPA emission data for CB-IV and RADM2 chemistry • Emission reduction simulation: . 50 % reduction in elevated SOx . 50 % reduction in elevated SOx and 50% in elevated NOx

  4. MEASUREMENTS • TEOM hourly PM 2.5 measurements – 15 sites in the modeling domain • SEARCH network -- daily 24-hour PM 2.5, sulfate, nitrate • IMPROVE (MANE-VU) network -- twice a week 24-hour PM 2.5, sulfate and nitrate

  5. Modeling Domain and Monitor Sites

  6. Daily averaged PM 2.5 concentrations on July 15, 1999(A) CB-IV; (B) RADM2 (B) (A)

  7. Daily averaged percentage of Sulfate to the total PM mass,(A) CB-IV; and (B) RADM2 (B) (A)

  8. Daily averaged percentage of Nitrate to the total PM mass,(A) CB-IV; and (B) RADM2 (B) (A)

  9. TEOM HOURLY DATA COMPARISON • Scatter plots • Diurnal plots • Statistics

  10. Averaged over 15 TEOM sites

  11. Comparison with 24-hour data from SEARCH and IMPROVE (MANE-VU)

  12. Comparisons with SEARCH data

  13. Compariosn with IMPROVE (MANE-VU) data

  14. EMISSION REDUCTION SIMULATUIN • 50% reduction of elevated SOx emissions • 50% reduction of elevated SOx emissions and 50% reduction of elevated NOx emissions

  15. Percentage reduction of PM 2.5 Concentration at 50% reduction of elevated SOx emission, (A) CB-IV; and (B) RADM2 (B) (A)

  16. Percentage reduction of PM 2.5 concentration at 50% reduction of elevated SOx emission and 50% reduction of elevated NOx emission, (A) CB-IV; and (B) RADM2 (A) (B)

  17. SUMMARY • Both CB-IV and RADM2 overpredicted hourly TEOM PM 2.5 measurements • RADM2 chemistry predicted much higher PM 2.5 concentrations than CB-IV • CB-IV based simulations showed relatively lower sulfate and higher nitrate compared to those of RADM2 • RADM2 chemistry is more sensitive in response to emission reductions than CB-IV

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