1. Recent Updates in v6.40
Chris Emery, Bonyoung Koo, Prakash Karamchandani, Gary Wilson, Greg Yarwood
March 2, 2017

2. Outline Sponsored updates Miscellaneous updates
Condensed halogen chemistry (TCEQ)
Gas/PM chemistry and wet deposition updates (EPA)
Parallel updates in OSAT/PSAT and DDM
Land/ocean mask to support oceanic halogen emissions
Miscellaneous updates
ACM2 solver speed
Landuse-dependent snow parameters
Anthropogenic & biogenic SOA precursors in VBS

3. Updates in CAMx v6.4 Condensed Halogen Chemistry (TCEQ)
Issue
Oceanic halogen emissions are important for ozone depletion
CB6r2h (v6.2) adds 88 reactions involving 40 I, Br, Cl species
Approach
CB6r reaction mechanism involving 9 Ix species (I-16b)
Most important Ix reactions determined from DDM rate sensitivity analysis
Add in-line Ix emissions = f(O3, SST, wind speed)
Ix emission fluxes output to deposition file for diagnostics/reporting
CB6r2h and I16-b result in similar ozone decrements (~5 ppb) over the Gulf of Mexico

4. Updates in CAMx v6.4 Condensed Halogen Chemistry (TCEQ)
Schematic of the full iodine chemistry mechanism (I-30) in CB6r2h.

5. Updates in CAMx v6.4 Condensed Halogen Chemistry (TCEQ)

6. Updates in CAMx v6.4 Chemistry Updates (EPA)
CB6r4 photochemistry
Combine I-16b halogen mechanism + CB6r3
CB6r3 (v6.3): T/P dependent organic nitrate branching from alkanes
Important for cold/high altitude photochemical applications
Add pseudo-heterogeneous hydrolysis of isoprene-derived organic nitrate (INTR)
INTR hydrolysis to HNO3 can be an important NOx loss pathway
Add heterogeneous sulfate chemistry on fine crustal aerosols
Negligible/minor sulfate impacts typically; larger impacts with high dust
CB6 halogen chemistry (CB6r2h and I-16b) is disproportionately slow
Inorganic Ix reactions are numerically “stiff” to solve
Fast EBI solver for I species and improved EBI performance overall by ~20%

7. Updates in CAMx v6.4 Chemistry Updates (EPA)
EPA 2011 Modeling Platform (July 28, 2015 NODA)
CB6r4 1-hr O3 performance statistics (40 ppb cutoff) for July 2011
NMB (%)
NME (%) R
Region
CB6r2
CB6r4
Change
Northwest
2.3
1.6
-0.7
13.2
0.90
California
-2.6
-3.7
-1.1
16.9
16.7
-0.2
0.75
0.77
+0.02
Rockies
1.0
0.6
-0.4
11.1
0.71
Southwest
-8.5
-9.1
-0.6
16.0
16.3
+0.3
0.51
0.50
-0.01
Northern Plains
9.2
8.0
-1.2
15.6
15.2
0.73
0.72
Southern Plains
8.6
6.2
-2.4
18.7
17.8
-0.9
0.68
0.70
Midwest
10.5
-1.3
14.9
0.74
Southeast
21.3
18.9
23.7
21.8
-1.9
Northeast
8.9
7.4
-1.5
14.4
13.6
-0.8
0.85

8. Updates in CAMx v6.4 Chemistry Updates (EPA)
1-hr O3 at 4 rural sites along Gulf coastline, July 2011
CB6r2
CB6r4

9. Updates in CAMx v6.4 Chemistry Updates (EPA)
1-hr O3 at 4 rural sites along Atlantic coastline, July 2011
CB6r2
CB6r4

10. Updates in CAMx v6.4 Chemistry Updates (EPA)
Land/ocean mask
Necessary to ensure that in-line Ix emissions are emitted from ocean bodies only
Removed from O3MAP file (optional field)
Now explicitly defined in the landuse file
LU = 1: “water” Historically all water coverage was assigned here
Now used for ocean coverage
LU = 3: “lake” Historically empty
Now used for fresh water
A "watermask" program allows for converting LU files if needed
WRFCAMx may or may not be able to make this distinction
Depends on LU database used in WRF

11. Updates in CAMx v6.4 Chemistry Updates (EPA)
SOAP organic aerosol chemistry
Remove 3 CG-SOA pairs and SOAH (17 species reduced to 10)
2 anthropogenic CG-SOA pairs by volatility (aromatics)
2 biogenic CG-SOA pairs by volatility (isoprene and terpenes)
2 non-volatile products (SOPA for anthropogenic and SOPB for biogenic)
Add anthropogenic IVOC precursor (but not for biogenics due to greater uncertainties)
Add aqueous SOA pathway from biogenic isoprene products (glyoxal)
Literature update for SOA yields, saturation, water solubility
You can still run CAMx with the original parameters
Higher SOA with updated parameters – SOAP2 (over predictions)
Lower SOA with original parameters – SOAP (under predictions)

12. Updates in CAMx v6.4 Chemistry Updates (EPA)
Total SOA averaged over July 2011
SOAP (v6.3)
SOAP2 – SOAP (v6.3)
SOAP (v6.4) – SOAP (v6.3)
SOAP2+newH – SOAP2

13. Updates in CAMx v6.4 Chemistry Updates (EPA)
Total OC MPE over July 2011
SOAP (v6.3) SOAP2 SOAP2+newH
SOAP (v6.3) SOAP (v6.4)

14. Updates in CAMx v6.4 Chemistry Updates (EPA)
RADM-AQ aqueous PM chemistry
Literature update for metal-catalyzed and peroxide sulfate oxidation
Mostly minor impacts to sulfate concentrations
SO2: v6.4 – v6.3 June 20, 2011
PSO4: v6.4 – v6.3 June 20, 2011

15. Updates in CAMx v6.4 Chemistry Updates (EPA)
Probing Tools
Tie in CB6r4 into OSAT and H/DDM
OSAT accounts for an additional ozone destruction pathway by iodine and conversion of nitrogen tracer classes involving iodine nitrate (INO3)
No change to tracer number, so OSAT runtimes are not be affected
Tie in CB6r4, SOAP and RADM-AQ updates into PSAT (PM-DDM updates forthcoming)
SOAP update reduces OA tracers, so PSAT will run faster for OA class

16. Updates in CAMx v6.4 Wet Deposition Update (EPA)
Formulation/efficiency improvements (more removal, less “vertical transport” of semi-soluble species)
June 20, 2011

17. Updates in CAMx v6.4 Wet Deposition Update (EPA)
June 20, 2011

18. Updates in CAMx v6.4 Miscellaneous Updates
ACM2 solver speedup as in CMAQ v5.1
CAMx/ACM2 runtimes are now similar to the default K-theory option.
Extend ACM2 to work with H/DDM (has always worked with SA)
Internal landuse-dependent snow parameters
Changes for urban and shrub land to increase snow cover (and thus albedo) for a given snow depth
Based on results reported by the Utah DAQ
Simplified anthropogenic vs. biogenic VBS SOA classification
Reflects the fact that aromatic precursors are mostly anthropogenic and isoprene and terpenes are mostly biogenic
No impact to SOAP, no impact on VBS model results
Use the updated PREPVBS tool to develop VBS emission inputs

19. Thank you