1. Sensitivity Analysis of Ozone in the Southeast
Daniel Cohan, Yongtao Hu,
Amir Hakami, and Ted Russell
Models-3 Users’ Workshop
October 27, 2003

2. Fall-Line Air Quality Study
CMAQ-DDM-3D, v.4.3:
Chemistry: SAPRC-99
Diffusion: Eddy diffusivity, with modified Kzz limits
DDM-3D: 1st and 2nd order; gas-phase only
Emissions (SMOKE):
NET-99 projected to 2000
BEIS-3 biogenics
CEM for point sources
Enhanced inventory for GA
Meteorology (MM5 v.3.5.3):
August 11-20, 2000
OSU/Eta LSM, MRF PBL
36-km resolution
12-km resolution

3. DDM and Brute Force ∆Ci a1 Dpj Conc. (e.g., O3) Sens. Parameter
(e.g., VOC Emissions)
Dpj

4. Decoupled Direct Method 3D
Concentrations
(t)
Concentrations
(t+Δt)
Chemistry
Advection &
Diffusion
I.C., B.C.,
Emissions
Chemistry
Sensitivities
(t)
Sensitivities
(t+Δt)

5. DDM Statistical Agreement: r2 of DDM vs. Brute Force (+/- 10% NOx)

6. Peak Hour Ozone and its Sensitivities
(sens. scaled to 100%E)
Sens to
NOx
Ozone Concentrations
Sens To
VOC
2nd
Ord.
Sens to
NOx
5pm EDT, Aug. 17, 2000
(max. observed = 173 ppb)

7. Downtown Atlanta: Ozone & its sensitivities, Aug. 11-20, 2000

8. Macon: Ozone & its sensitivities, Aug. 11-20, 2000

9. Variability of Ozone Sensitivity to NOx
(Hourly Average +/- 1, in ppmv,
Aug , 2000)

10. Ozone Sensitivity to NOx: Domainwide v. Local Emissions
Zero
line

11. Taylor-Series Expansion: Decomposing Changes in Ozone
O3,A
1st-Order:
E * S1
2nd-Order:
0.5(E)2 * S2
O3,B B EB
Emissions EA

12. Reduction in Ozone due to 50% Reduction in NOx & VOC
Error: DDM 1st Order only
Reduction in Ozone due to
50% Reduction in NOx & VOC
Ozonebase – Ozone50%emis
… with 2nd order
5pm EDT, Aug. 17, 2000

13. 50% Reduction in NOx and VOC
Ozone Reduction for
50% Reduction in NOx and VOC
8-day average: Aug , 2000

15. Ozone Isopleths at Peak Hour
Atlanta
Macon
Ozone (ppmV)
August 17, 2000
(from the method of Hakami et al., 2003)

16. Conclusions
CMAQ-DDM-3D accurately computes 1st and 2nd order gas-phase sensitivities.
Aerosol sensitivities in progress.
Include DDM-3D in future releases of CMAQ?
Ozone primarily NOx-limited during episode.
VOC sensitivity confined to urban cores.
Response to local and regional NOx emissions can differ.
Non-linearities affect ozone response to large perturbations in emissions.
Using linear term alone underestimates benefit of large NOx reductions.
Ignoring cross sensitivities overestimates benefit of joint NOX-VOC reductions in cities.
Ongoing work:
Further explore sensitivity to point & local emissions.
Economic optimization of control strategies.