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 Source evaluation of aerosol precursors with the adjoint of GEOS-Chem

Forward sensitivity

Adjoint sensitivity

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.

Model Description, v (Bey et al., 2001; Park et al., 2004) GEOS-3 Assimilated meteorology 4°x5°(Global) resolution, 30 vertical levels HO x - NO x - HC full gas-phase chemistry Aerosols - Secondary inorganic - Carbonaceous (primary) aerosol - Sea salt - Dust Forward Model: GEOS-CHEM Gas-phase emissions SO 2, NO x, NH 3 Aerosol SO 4 2-, NO 3 -, NH 4 + Gas-phase chemistry Cloud processing Aerosol thermo

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 The adjoint of GEOS-Chem: hybrid 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) Henze et. al, 2007 Resources - CPU: t adj ~ 1.5 t fwd As || as the fwd model - HD: 45 GB for 1 month (4x5)

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

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

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

GEOS-Chem Adjoint: full chemistry Initial Conditions (all species and tracers) Emissions sectors - NO x (lightning, anthro) - SO x (anthro, bioburn, biofuel, ships) - NH 3 (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

Pollution = non-attainment of NAAQS for PM 2.5 of 15 µg/m 3 (annual ave)

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.

Attainment -- Aerosols Define cost function ~ non-attainment for PM 2.5 July 2001 NH 4 + non-attainment

Attainment -- Aerosols Define cost function ~ non-attainment for PM 2.5 NH 4 + non-attainment Emissions (normalized)Sensitivities (normalized) anth NH 3 Responsibility Effectiveness Benefit (Hakami et al., 2006)

Attainment -- Aerosols Seasonal variability July Emissions Sensitivities anth NH 3 stack SO x April NH 3 controls effective in spring, SO 2 in summer. Also consider $$ (Pinder et. al, 2007)

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

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.

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

Inverse Model Parameter Estimate Predictions Adjoint Forcing Gradients (sensitivities) Optimization Forward ModelAdjoint Model Observations Improved Estimate - t0t0 tftf tftf t0t0 Inverse Modeling using Adjoint Model

Emissions Scaling Factors DIFF(GC-IMPRV) NIT Domain wide NH 3 adjustments similar to inverse modeling study by Gilliland et al., Optimized Anth NH [kg/box/s]... scaling f = ln( e 10 /e 1 )

Emissions Scaling Factors NH 4 + CASTNet Optimized Anth NH [kg/box/s]... scaling f = ln( e 10 /e 1 )

The End Thanks!