Evaluation of Aerosol Precursors with the Adjoint of GEOS-Chem

1. Source evaluation of aerosol precursors with the adjoint of GEOS-Chem Daven K. Henze with Amir Hakami and John H. Seinfeld Caltech, Chemical Engineering Support from: NSF, EPA, TeraGrid and JPL Supercomp., W. & S. Davidow Fellowship

2. Forward sensitivity

3. Adjoint sensitivity

4. Adjoint method Depending on “model response,” can be used for: Sensitivity analysis: quantifying influence of uncertain model parameters (emissions, reaction rates, …) Attainment studies: assessing the effectiveness of emissions abatement Inverse modeling: using large data sets, optimizing parameters on resolution commensurate with forward model.

5. Gas-phase chemistry Cloud processing Aerosol thermo Gas-phase emissions SO2, NOx, NH3 Aerosol SO42-, NO3-, NH4+ Forward Model: GEOS-CHEM Model Description, v6-02-05 (Bey et al., 2001; Park et al., 2004) • GEOS-3 Assimilated meteorology • 4°x5°(Global) resolution, 30 vertical levels • HOx - NOx - HCfullgas-phase chemistry • Aerosols - Secondary inorganic - Carbonaceous (primary) aerosol - Sea salt - Dust

6. The adjoint of GEOS-Chem: hybrid • Discrete (adjoint of algorithm) • KPP (Damian et al., 2002; Sandu et al., 2003; Daescu et al., 2003) • - chemistry • TAMC(Giering & Kaminski, 1998) and manual • - aerosol thermo • - cloud processing • - convection • Manual • - turbulent mixing • - deposition • - heterogeneous chemistry • Continuous (adjoint of equation) • - advection(Vukicevic et al., 2001; Thuburn and Haine, 2001; Liu and Sandu, 2006; Hakami et al., 2006; Singh et al., 2006) Resources - CPU: tadj ~ 1.5 tfwd As || as the fwd model - HD: 45 GB for 1 month (4x5) Henze et. al, 2007

7. Testing the Adjoint Model: Gradient Check Check gradient using finite difference calculation cost function control parameter adjoint sensitivity Component-wise analysis affords domain wide points-of-comparison

8. Testing the Adjoint: single processes, 1 week (thermo only)

9. Testing the Adjoint: single processes, 1 week (thermo only) (chem only)

10. GEOS-Chem Adjoint: full chemistry Initial Conditions (all species and tracers) Emissions sectors - NOx (lightning, anthro) - SOx (anthro, bioburn, biofuel, ships) - NH3 (anthro, bioburn, biofuel, natural) - OC/BC (anthro, bioburn, biofuel) - others are easy to add Reaction rate constants - All reactions - gas-phase emissions (NO, ISOP, ACET, etc.) - dry deposition

11. www.epa.gov Pollution = non-attainment of NAAQS for PM2.5 of 15 µg/m3 (annual ave)

12. Adjoint method Depending on “model response,” can be used for: Sensitivity analysis: quantifying influence of uncertain model parameters (emissions, reaction rates, …) Attainment studies: assessing the effectiveness of emissions abatement Inverse modeling: using large data sets, optimizing parameters on resolution commensurate with forward model.

13. NH4+ non-attainment July 2001 Attainment -- Aerosols Define cost function ~ non-attainment for PM2.5

14. Benefit (Hakami et al., 2006) anth NH3 Emissions (normalized) Sensitivities (normalized) Responsibility Effectiveness Attainment -- Aerosols Define cost function ~ non-attainment for PM2.5 NH4+ non-attainment

15. April NH3 controls effective in spring, SO2 in summer. Attainment -- Aerosols Seasonal variability Emissions Sensitivities anth NH3 stack SOx July Also consider $$ (Pinder et. al, 2007)

16. Attainment -- Aerosols Long range transport Emissions Sensitivities w.r.t. surface SOx Influences concentrations, not AQ attainment Future emissions scenarios? Climate change? Cost?

17. Adjoint method Depending on “model response,” can be used for: Sensitivity analysis: quantifying influence of uncertain model parameters (emissions, reaction rates, …) Attainment studies: assessing the effectiveness of emissions abatement Inverse modeling (Data Assimilation): using large data sets, optimizing parameters on resolution commensurate with forward model.

18. Model: Diff: MOD - OBS Observed Aerosol (IMPROVE): January 2002 SO4 NIT Observed:

19. Inverse Modeling using Adjoint Model Inverse Model Optimization Improved Estimate Parameter Estimate Gradients (sensitivities) Forward Model Adjoint Model t0 tf tf t0 Predictions Adjoint Forcing - Observations

20. Optimized Anth NH3 1 . . . 10 [kg/box/s] scaling f = ln( e10/e1) Emissions Scaling Factors NIT DIFF(GC-IMPRV) 1 . . . 10 Domain wide NH3 adjustments similar to inverse modeling study by Gilliland et al., 2006.

21. Optimized Anth NH3 1 . . . 10 [kg/box/s] scaling f = ln( e10/e1) Emissions Scaling Factors NH4+ CASTNet

22. The End Thanks!