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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
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. v2.110-day Summer Test Case (new ? old)
12. ISORROPIA v1.7 vs. v2.110-day Winter Test Case (new ? old)
13. ISORROPIA v1.7 vs. v2.1Test of Numerical Stability
14. Add New Species to CMAQ: Mg, K, CaStep 1. Anthropogenic PM2.5
19. CMAQ Results10-day Winter Test Case (new ? old)
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.
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