Attributing direct radiative forcing to specific emissions using adjoint sensitivities Daven K Henze, Drew T. Shindell, Robert J. D. Spurr g-con

Radiative Forcing Transfer Functions How to calculate the radiative forcing change for a given change in emissions? IPCC, 2007 Global contributions to aerosol direct RF

Radiative Forcing Transfer Functions How to calculate the radiative forcing change for a given change in emissions? Using transfer function T :

Radiative Forcing Transfer Functions How to calculate the radiative forcing change for a given change in emissions? Using transfer function T : Approximate T using adjoint: Calculated using GC adjoint (Henze et al., 2007 and LIDORT (Spurr, 2002)

Radiative Forcing Transfer Functions The % change in radiative forcing per change in BC emission: note: per change in any BC emission. This shows variation in efficiency of BC emissions forcing.

Radiative Forcing Transfer Functions The % change in radiative forcing per change in SO 2 emission:

Applying to MFR 2030 – 2000 inventories BC, Total SO 2, Total

Applying to MFR 2030 – 2000 inventories BC, Total SO 2, Total

Applying to CLE 2030 – 2000 inventories BC, Total SO 2, Total

Applying to CLE 2030 – 2000 inventories BC, RESALL SO 2, RESALL

Applying to CLE 2030 – 2000 inventories BC, POWER SO 2, POWER

Validation: BC CLE 2030 – 2000 perturbation Looks good

Validation: SO 2 CLE 2030 – 2000 perturbation Looks OK, but adjoint-approach biased?

Validation: SO 2 10% perturbationsCLE 2030 – 2000 perturbation Check: does reducing perturbation reduce nonlinearity? Yes. The adjoint code is accurate.

Validation: SO 2 RF E SO2 E 2000 E’ 2030 |ADJ| > |FD| E’’ 2030 |ADJ| < |FD| Can we anticipate bias?

Validation: SO 2 CLE 2030 – 2000 perturbation E 2030 > E 2000 (China, India) E 2030 < E 2000 (Europe ) Yes, bias can be anticipated. Also, overall ordering remains the same. Conclusion: adjoint sensitivities provide a rapid means of exploring the effect of specific emissions changes on aerosol DRF.

The end Thanks to: Columbia Univ. Earth Institute Fellowship Drew Shindell, Rob Spurr, Nadine Unger, John Seinfeld NASA GSFC: NCCS NASA JPL: SCC

Radiative Transfer Code Mie Code derivate mode GC Adj Weighting functions Henze et al., 2007 Following Martin et al., 2004, Drury et al., 2008 Radiative Forcing with GEOS-Chem GEOS-Chem Mie Code Grainger et al., 2004 [SIA], [BC], RH, D dry Radiative Transfer Code LIDORT (Spurr, 2002) TOA upward SW flux Forward model Sensitivity calculation:

Radiative Forcing with GEOS-Chem GEOS-Chem [SIA], RH 8.4Koch et al. (1999) 11Chin et al. (2002) Martin et al. (2004) 10.5current work Literature D dry N, D wet Mie Code Grainger et al., 2004 (tabulate as )

Validating Radiative Forcing Sensitivity ignore Phase function coefficients for SIA(D wet ) D max D min

Validating Radiative Forcing Sensitivity Mie results for extinction at discrete mode diameters:

Radiative Forcing (forward calculation) Chemical Transport Model Mie Code Aerosol concentrations optical properties

Radiative Forcing Sensitivity LIDORT Spurr, 2002 Jacobian calculation GEOS-Chem Adj Henze et al., 2007 Mie Derivative [SIA]*, [BC]* Grainger et al., 2004

Radiative Forcing (forward calculation) Chemical Transport Model Mie Code Aerosol concentrations optical properties Radiative Transfer Code TOA upward SW fluxes

Next Steps -Validate the transfer functions -Apply to various emissions perturbations of interest

Radiative Forcing Sensitivity Radiative Transfer Code LIDORT (Spurr 2002) Jacobian calculation GEOS-Chem Adj Mie Derivative [SIA]*, [BC]* 24 hr 1 week

Radiative Forcing with GEOS-Chem GEOS-Chem N, D wet Mie Code Grainger et al., 2004 [SIA], RH [BC] D dry (external mixture) Radiative Transfer Code LIDORT (Spurr, 2002) TOA upward SW flux Following Martin et al., 2004; Drury et al,. 2008

Following Martin et al., 2004, Drury et al., 2008 Radiative Forcing with GEOS-Chem GEOS-Chem Mie Code Grainger et al., 2004 [SIA], [BC], RH, D dry Radiative Transfer Code LIDORT (Spurr, 2002) TOA upward SW flux Forward model Radiative Transfer Code Mie Code derivate mode GEOS-Chem Adj Sensitivity calculation [SIA]*, [BC]* Weighting functions Henze et al., hr 1 wk

Applying to CLE 2030 inventories note: this takes about 10 seconds

Applying to MFR 2030 inventories