Regional Modeling Update and Issues

1. California Environmental Protection Agency Air Resources Board Regional ModelingUpdate and Issues Luis F. Woodhouse, Ph.D. May 6, 2003

2. Emissions and Meteorology Microscale Modeling Regional Modeling Integrated Results Risk Assessment Mapping and Visualization

3. Outline • Review of last meeting • Regional modeling update • Model evaluation • Comparison with previous studies • Integrating microscale and regional modeling • Future analysis • Future statewide modeling considerations 3

4. Review of Last Meeting (September 12, 2002) • Previous studies • UAM and CAMx with Carbon Bond IV • Select toxics • Small domain • Present study • CALGRID and CMAQ with SAPRC99 • Over 30 toxics • Large domain • Note: CAMx not used since it’s implementation mechanism software is not publicly available 4

5. 1,3-butadiene Formaldehyde Acetaldehyde Acrolein Benzene Carbon tetrachloride Chloroform Dichloromethane 1,2-Dichloroethane o-Dichlorobenzene p-Dichlorobenzene Ethylene oxide Styrene Toluene Vinyl Chloride Xylenes Hexavalent Chromium Diesel PM10 PM10 Arsenic PM10 Beryllium PM10 Cadmium PM10 Lead PM10 Manganese PM10 Mercury PM10 Nickel PM10 Zinc Toxics 5

6. Ventura San Bernardino Los Angeles Riverside Orange San Diego 93,264 km2 87 x 67 grids (4 km x 4 km) Mexico Regional Modeling Domain Regional Modeling Domain 6

7. Model Inputs • Emissions • SCOS97 adjusted to 1998 • seasonal inventories (weekday/weekend) • latest profiles, surrogates, and EMFAC2000 (with DTIM4) • Meteorology • CALMET: diagnostic model using data from over 200 sites • MM5: prognostic model • Boundary conditions • same for each month, based on SCOS97 7

8. Regional Modeling Update • CALGRID • January 1 to December 31, 1998 • CMAQ • January, April, August and November 1998 8

9. Model Performance • Verify model’s ability to reproduce measured concentrations • Ozone: Performance standards are well established • Toxics: No established performance standards 9

10. Model PerformanceConclusions • Iterative process is needed to improve ozone performance • In general, model predicted annual average toxics concentrations are comparable with observations for most species • Results comparable with previous studies 10

11. Ozone Model Evaluation • Compared daily ratios of model-predicted to measured maximum ozone concentrations • CALGRID closer to observations • CMAQ over predicts 11

12. Ozone Model Evaluation (cont.) • Calculated daily average gross errors: • Measure model’s overall ability to reproduce observed hourly ozone at each site above a specified threshold concentration • Iterative process 12

13. Toxic VOCs Model Evaluation • Annual average concentrations • In general, model predictions are comparable with the measured annual concentrations for most toxics VOC species • Some species are significantly under predicted by both models: carbon tetrachloride, chloroform, ethylene chloride, styrene 13

14. Annual Averages of Toxic VOCs 14

15. Annual Averages of Toxic VOCs 15

16. Annual Averages ofInert Toxics • Diesel PM10 • Model predictions are comparable to observed elemental carbon results • Hexavalent Chromium • Model predictions are below detection limit • PM10 components • Performance depends on species 16

17. Annual Average of Inert Toxics * 17 * DIES in ug/m3 compared to elemental carbon

18. Annual Average of Inert Toxics * * * 18 * DIES in ug/m3 compared to elemental carbon

19. CALGRID (1998) Diesel PM10 Benzene ppb μg/m3 19

20. Comparison withPrevious Studies • MATES II • April 1998 to March 1999 field study • Models • UAM and recently CAMx • Carbon Bond IV reaction mechanism • Our results are comparable 20

21. Comparison with MATES IIBenzene 21

22. Comparison with MATES IIDiesel PM10 vs. Elemental Carbon 22

23. Comparison with MATES IIFormaldehyde 23

24. Integrating Microscale and Regional Modeling Results • Microscale modeling estimates near source impacts (meters) • Regional modeling estimates impacts from sources in a large area (km) • Issue • double-counting 24

25. Barrio Logan Modeling Results DIESEL PM10 ISCST3 CALINE CALGRID BARRIO CHULA EL -----------BARRIO LOGAN-------------- LOGAN VISTA CAJON 25

26. Barrio Logan Modeling Results (cont.) BENZENE ISCST3 CALINE CALGRID BARRIO CHULA EL -----------BARRIO LOGAN-------------- LOGAN VISTA CAJON 26

27. Barrio Logan Modeling Results (cont.) HEXAVALENT CHROMIUM NA ISCST3 CALINE CALGRID BARRIO CHULA EL ---------BARRIO LOGAN-------------- LOGAN VISTA CAJON 27

28. Sensitivity Simulations Double Counting* • In Barrio Logan, local emissions contribute less than 1% of the annual average concentration of most toxic species. • In Wilmington, local emissions contribute 15%-90% of the annual average concentrations • Benzene (47%) • Diesel exhaust (40%) • 1,3-butadiene (16%) 28 * simulations for all 1998 were done in each case with CALGRID

29. Sensitivity SimulationsBarrio Logan • Changing boundary conditions has very small impact on annual average toxic concentrations • Choosing different averaging periods • 12-month average toxic concentrations can be significantly different from 4-month average concentrations • 4-month average cumulative risk is about 10% higher than the 12-month average cumulative risk 29

30. Future Analysis • Improve estimates of background toxic concentrations • Omit all toxics emissions in a cell • Omit toxic emissions from selected categories in a cell • Evaluate procedures for estimating contributions of secondary species • Evaluate deposition effect • Run CALGRID using MM5 winds • Conduct spatial analysis 30

31. Future Statewide Modeling Considerations • Air quality model selection • CALGRID, CMAQ, CAMx, other • Atmospheric reaction mechanism • Run time (e.g., CALGRID with SAPRC99 and 4 km x 4 km grids, at least 6 months) • Period simulated • Every day in a year or selected episodes 31

32. Future Statewide Modeling Considerations (cont.) • Input preparation • Emissions • Meteorology (CALMET, MM5) • Other considerations • Baseline year • Multiple year simulation • Storage requirements 32