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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 CMAQs 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