Impact of ISORROPIA II on air quality model predictions
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Impact of ISORROPIA II on air quality model predictions

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1. Overview. What is ISORROPIA?Motivation for ISORROPIA IIImplementation in CMAQ v5.0?model results interspersed throughoutSummary
Impact of ISORROPIA II on air quality model predictions

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1. October 25, 2011 Prakash Bhave, Golam Sarwar, Havala Pye, George Pouliot, Heather Simon, Jeffrey Young, Chris Nolte, Ken Schere, Rohit Mathur U.S. Environmental Protection Agency CMAS Conference Chapel Hill, NC October 24 ? 26, 2011 Impact of ISORROPIA II on air quality model predictions

2. Overview What is ISORROPIA? Motivation for ISORROPIA II Implementation in CMAQ v5.0? model results interspersed throughout Summary & Future Work

3. What is ISORROPIA?

4. What is ISORROPIA? Schematic of PM species in CMAQ?s AE5 module ISORROPIA I treats SO4/NO3/NH4/Na/Cl/H2O system

5. Why ISORROPIA II? Motivation #1: Numerical Stability

6. Why ISORROPIA II? Motivation #2: Coarse NO3 Bias

7. Why ISORROPIA II? Optimized activity coefficient calculations to minimize model runtime and improve numerical stability Treats thermodynamics of crustal materials Mg2+, K+, Ca2+ MgSO4, Mg(NO3)2, MgCl2, K2SO4, KHSO4, KNO3, KCl, CaSO4, Ca(NO3)2, CaCl2 Peer-reviewed literature: Fountoukis & Nenes (ACP, 2007) ISORROPIA versions released in CMAQ

8. Implementation in CMAQ v5.0?

9. Implementation in CMAQ v5.0? Revised coarse-mode mass transfer (new species shown in red)

10. Implementation in CMAQ v5.0? Compare ISORROPIA v2.1 versus v1.7 Evaluate numerical stability Add new species to CMAQ: Mg, K, Ca

11. ISORROPIA v1.7 vs. v2.1 10-day Summer Test Case (new ? old)

12. ISORROPIA v1.7 vs. v2.1 10-day Winter Test Case (new ? old)

13. ISORROPIA v1.7 vs. v2.1 Test of Numerical Stability

14. Add New Species to CMAQ: Mg, K, Ca Step 1. Anthropogenic PM2.5

19. CMAQ Results 10-day Winter Test Case (new ? old)

20. Summary Compared to v1.7, ISORROPIA v2.1 ? is more numerically stable! puts slightly more NO3- in the gas phase during summer. puts slightly more NO3- in particle phase during winter. ISORROPIA v2.1 is fully implemented in CMAQ v5.0, taking advantage of its capabilities to handle Mg, K, & Ca. In CMAQv5.0, coarse-mode NO3 increases inland, at the expense of fine NO3. Future Work Evaluate CMAQv5.0 against impactor measurements Refine estimates of coarse PM emissions Explore computational burden of v2.1 ? prelim analysis suggests 12% slowdown 19

21. 20 Appendix

22. CMAQ details CMAQv4.7.1 uses ISORROPIA 1.7 Implemented ISORROPIA 2.1 in CMAQv4.7.1 Test period covered for 10 days in 2002 January - winter July - summer Continental US domain with 36-KM grid-cells Used same IC and BC Several tests were conducted (with ISORROPIA 1.7 & ISORROPIA 2.1) Normal emissions (without Ca, Mg, and K) Sensitivity runs by doubling EC emission in one grid-cell in Massachusetts Normal emissions + Ca, Mg, and K; however these were not included in ISORROPIA Normal emissions + Ca, Mg, and K; these were included in ISORROPIA


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