1. Division of Air Quality Utah Department of Environmental Quality PM 2.5 24-Hour NAAQS Modeling Issues in the State of Utah WRAP Workshop on Regional Emissions and Air Quality Modeling Studies July 30, 2008 Patrick Barickman Tyler Cruickshank

2. Division of Air Quality Utah Department of Environmental Quality Overview Effect of mountain/valley topography Specifics of Utah Nonattainment areas The nature of PM 2.5 formation in Northern Utah during winter inversions Modeling issues and challenges Met modeling Episode selection Local chemistry Summary

3. Division of Air Quality Utah Department of Environmental Quality Boise Salt Lake City Uintah Basin Upper Green River Basin

4. Division of Air Quality Utah Department of Environmental Quality Population: 2,040,000 75% of State Population: 110,000

5. Division of Air Quality Utah Department of Environmental Quality PM 2.5 Monitoring Network Nat. Speciation Network – Every 3 or 6 days

6. Division of Air Quality Utah Department of Environmental Quality Influence of Mountain/Valley Topography on Ambient Concentrations Cache Valley 70 miles Cache County, UT & Franklin County, ID

7. Division of Air Quality Utah Department of Environmental Quality Cache Valley Winter Inversions Influence Air Quality January 15, 2004 24-hour average PM2.5 = 132.5 ug/m3

8. Division of Air Quality Utah Department of Environmental Quality Wasatch Front – Prone To Inversions But Far Less Contained Than the Cache Valley 94 miles

9. Division of Air Quality Utah Department of Environmental Quality Northern Wasatch Front Nonattainment Area – Salt Lake City

10. Division of Air Quality Utah Department of Environmental Quality PM 2.5 Formation In Northern Utah During Winter Inversions

11. Division of Air Quality Utah Department of Environmental Quality Exceedences 80% < 50 ug 65% < 50 ug PM 2.5 Concentrations PM 2.5 Network Observations 2005 - 2008

12. Division of Air Quality Utah Department of Environmental Quality PM2.5 Species Composition National Speciation Network, Sampled Every Third or Sixth Day December – February 2000 – 2007 Individual Day February, 2004 Wasatch Front

13. Division of Air Quality Utah Department of Environmental Quality Two Week Period Cache Valley – January, 2004 ug/m3

14. Division of Air Quality Utah Department of Environmental Quality Modeling issues and challenges

15. Division of Air Quality Utah Department of Environmental Quality MM5 Modeling Cooperative Agreement Between UDAQ and US Army Dugway Proving Ground Modeling actually done by NCAR UDAQ modeling domain adapted to match pre-existing domain projection Provides UDAQ with nested domains of 1.3 and 4 kilometer resolution

16. Division of Air Quality Utah Department of Environmental Quality Episode Selection - Constraints and Tradeoffs PM 2.5

17. Division of Air Quality Utah Department of Environmental Quality PM 2.5

18. Division of Air Quality Utah Department of Environmental Quality CMAQ and Winter Chemistry Weakness with the formation of nitric acid in sub-freezing conditions with snow cover Nitric acid production – problems with the chemistry solver Night-time pathway ( Prakash Bahave – EPA ) Daytime albedo Researchers at USU have measured rapid ammonium nitrate production through new pathways – not even in the chemistry solver

19. Division of Air Quality Utah Department of Environmental Quality Summary Science Winter time exceedences of the 24-hour PM2.5 NAAQS show a complex set of interactions Our analysis indicates the need for improvements in the CMAQ chemistry for these conditions

20. Division of Air Quality Utah Department of Environmental Quality Summary Policy New (lower) NAAQS involve larger areas and more people affected by SIPs If small incremental benefits in air quality come at a relatively high cost, then, Model performance, as technical justification to bear those costs, becomes increasingly important Atmospheric chemistry of ammonium nitrate, especially, suggests co-benefits for ozone control strategies

21. Division of Air Quality Utah Department of Environmental Quality Summary SIP technical support could go well beyond specific modeling analyses for particular nonattainment areas Implications for the WRAP Regional Modeling and Analysis Center Science questions to improve model performance in western US could be addressed A resource for sub-components of the model ( met, emissions )