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Comprehensive Data Needs for Air Quality Model Evaluation

This research presents detailed data needs for evaluating radical and NOy budgets in SCOS97-NARSTO air quality model simulations, including equations, species definitions, photochemistry fundamentals, and model evaluation methodologies. The study emphasizes the significance of local and cumulative diagnostics for accurate model assessment and addresses uncertainties in CMAQ vs. CAMx comparisons.

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Comprehensive Data Needs for Air Quality Model Evaluation

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  1. Data Needs for Evaluation of Radical and NOy Budgets in SCOS97-NARSTO Air Quality Model Simulations Gail S. Tonnesen University of California, Riverside Bourns College of Engineering Center for Environmental Research and Technology February 14, 2001, SCOS97-NARSTO DataWorkshop

  2. Funding for related projects U.S. EPA American Chemistry Council Datasets Draft prerelease datasets provided by ARB Acknowledgments

  3. Trace Gas Governing Equations • j=1,N Coupled PDEs Cj t  v.Cj + D2Cj + P(C)  L(C)Cj + Ej  Dj • Operator Splitting: Cj t = v.Cj Cj t = D2Cj + Ej  Dj dCj dt = P(C)  L(C)Cj Gear solver is the gold standard for stiff ODEs

  4. Model Evaluation • Verification, Validation or Evaluation? • Oreskes et al., 1994. • Comparisons with ambient data. • Validation of component processes. • Indicators for testing O3 sensitivity. • Sensitivity and uncertainty analysis.

  5. Family Definitions NOx = NO + NO2 + (NO3 + 2 N2O5 + HONO + HNO4) NOz = HNO3 + RNO3 + NO3– + PAN NOy = NOx + NOz = total oxidized nitrogen. HC = VOC (or ROG) + CH4 + CO Ox = O3 + O + NO2 + NOz + 2 NO3 + 3 N2O5 + HNO4 HOx = OH + HO2 + RO2

  6. Fundamental Photochemistry Tropospheric gas phase chemistry is driven by the OH radical: • Radical Initiation • Radical Propagation • Radical Termination • NOx termination

  7. PSS Equilibrium NO2 + h  NO + O O + O2  O3 O3 + NO  O2+ NO2 NO2 + O3 NO3 + O2 NO3+ h  NO2 + O P(Ox): RO2 + NO  RO+ NO2 HO2 + NO  OH+ NO2

  8. Radical Initiation O3 + h  O(1D) O(1D) + H2O  2 OH HCHO + h 2 HO2 + CO HO2 + NO  OH+ NO2 HONO + h OH+ NO PAN  RO3+ NO2

  9. Radical Propagation OH + CH4 + O2 CH3 O2 + H2O CH3O2 + NO  NO2 + CH3O CH3O + O2 HO2 + HCHO HO2 + NO  NO2 + OH 2x( NO2+ h + O2 O3 + NO ) Net Reaction: CH4 + 4 O2 2 O3 + HCHO + H2O

  10. Radical and NOx termination OH + NO2  HNO3 HO2 + HO2 H2O2 HO2 + RO2 ROOH RO2 + NO RNO3 RO3 + NO2 PAN N2O5 + H2O  2 HNO3

  11. Model Evaluation • Local Diagnostics • Instantaneous reaction rates at a given site. • Examples: P(OH), P(Ox), P(Ox)/P(NOz) • Cannot get production rates from time-series! • Cumulative Trajectory Diagnostics • cumulative history of reaction rates and other loss processes in an air parcel integrated over hours or days. • Examples: [H2O2], [HNO3], [O3], [O3]/[NOz]

  12. Data Needs for Local Diagnostics • Radical Initiation J-values & HCHO, O3, H2O, HONO, H2O2, PAN • OH Chain Length  kOH HCi /( kOH HCi + kOH NO2 ) kHO2 NO /(kHO2 NO + kHO2 (RO2+ 2 HO2 ) ) • Radical Termination NO2 & OH, HO2 & RO2, NO & RO2, O3 • NOx Termination, P(NOz): NO2 & OH, NO & RO2, NO2 & RCO3, NO3, N2O5 & H2O • Pg(Ox) NO, HO2, RO2.

  13. Data Needs for Cumulative Diagnostics • Radical Initiation & Termination (approximate): (2 peroxides + NOz ) • OH Chain Length (approximate): Ox / (2 peroxides + NOz ) 2 peroxides/NOz • NOx Termination, P(NOz): HNO3, speciated RNO3, NO3-, PAN • P(O3), P(Ox): O3, & O3 +NO2 + NOz

  14. Model Domain and Parameters • 1997 Southern California Ozone Study (SCOS97). Aug 3 to 5, 1997 • CMAQ and CAMx • MM5 16 layers • CB4 chemical mechanism • Gear CMAQ, CMC CAMx • Bott Advection Scheme • No Aerosols • Includes process analysis diagnostic outputs.

  15. Timing in CAMx - are emissions calculated as PST or PDT? Vertical mixing - CAMx has less vertical dispersion in early morning? Emissions - CMAQ may be missing large point sources. Problem with isoprene in CAMx Uncertainties In CMAQ vs CAMx Comparison

  16. Peak Model Ozone on Aug 5 (3rd day) Difficult to analyze effects accumulated over 3 days, so...

  17. Start Evaluation with spinup (1st day) Comparison of O3 at 15:00 PDT:

  18. Comparison of O3 aloft before start of 2d day Errata: all units are ppbV

  19. Pg(Ox) 7:00-8:00 PDT

  20. Pg(Ox) 8:00-9:00 PDT

  21. Pg(Ox) 9:00-10:00 PDT

  22. Pg(Ox) 10:00-11:00 PDT

  23. Pg(Ox) 11:00-12:00 PDT

  24. Cumulative Pg(Ox) 7:00-19:00 PDT

  25. CO conc. at 9:00 PDT in LA: inversion breaks up 2 hours later in CAMx…is timing of emissions wrong?

  26. Cumulative P(OH) 7:00-19:00 PDT, Aug 3.

  27. H2O at 12:00 PDT

  28. % contribution of O1D to OH initiation, cumulative for Aug 3.

  29. HO2 initiation, cumulative for Aug 3.

  30. RO2 radical initiation, cumulative for Aug 3.

  31. Reactions of NO3 & O3 with isoprene, cumulative for Aug 3.

  32. Reactions of OH with isoprene, cumulative for Aug 3.

  33. Total new radical initiation, Layer 1, cumulative for Aug 3.

  34. Total OH Production, Layer 1, cumulative for Aug 3.

  35. HNO3 mixing ratio, 24:00 PDT, Aug 5.

  36. HNO3 produced by OH+NO2, Layer 1, cumulative for Aug 5.

  37. HNO3 produced by OH+NO2, Later 3, cumulative for Aug 5.

  38. HNO3 produced by N2O5+H2O, cumulative for Aug 5.

  39. E-W Slice through LA, cumulative for Aug 5.

  40. Fraction HNO3 of total NOz, cumulative for Aug 5.

  41. Net Production of PAN, cumulative for Aug 5.

  42. Production of organic nitrates, cumulative for Aug 5.

  43. Total Production of NOz, cumulative for Aug 5.

  44. Ox production efficiency per NOx, cumulative for Aug 5. (Note: regions of gray within red are areas in which P(NOz) is negative).

  45. Indicators based on HNO3 or NOz may fail in CAMx simulations due to large contribution of N2O5+H2O to P(HNO3). Alternative: Use indicators based on radical propagation efficiency, O3 is VOC sensitive for: %HO2+NO > 93% %OH+HC < 80% Indicators to Evaluate O3 Sensitivity

  46. Indicator of O3 sensitivity: %HO2+NO (cumulative for Aug 5).

  47. Indicator of O3 sensitivity: %OH+HC (cumulative for Aug 5). (Note colormap is inverted)

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