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 variationin efficiency of BC emissions forcing.

Radiative Forcing Transfer Functions

The % change in radiative forcing per change in SO2 emission:

Applying to MFR 2030 – 2000 inventoriesBC, Total SO2, Total

Applying to MFR 2030 – 2000 inventoriesBC, Total SO2, Total

Applying to CLE 2030 – 2000 inventoriesBC, Total SO2, Total

Applying to CLE 2030 – 2000 inventoriesBC, RESALL SO2, RESALL

Applying to CLE 2030 – 2000 inventoriesBC, POWER SO2, POWER

Validation: BC

CLE 2030 – 2000 perturbation

Looks good

Validation: SO2

CLE 2030 – 2000 perturbation

Looks OK, but adjoint-approach biased?

Validation: SO2

10% perturbationsCLE 2030 – 2000 perturbation

Check: does reducing perturbation reduce nonlinearity?

Yes. The adjoint code is accurate.

Validation: SO2

RF

ESO2E2000 E’2030

|ADJ| > |FD|

E’’2030

|ADJ| < |FD|

Can we anticipate bias?

Validation: SO2

CLE 2030 – 2000 perturbation

E2030 > E2000 (China, India)

E2030 < E2000 (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 Codederivate 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 CodeGrainger et al., 2004

[SIA], [BC], RH, Ddry

Radiative Transfer CodeLIDORT (Spurr, 2002)

TOA upward SW flux

Forward model Sensitivity calculation:

Radiative Forcing with GEOS-Chem

GEOS-Chem

[SIA], RH8.4 Koch et al. (1999) 11 Chin et al. (2002)6.5-13.9 Martin et al. (2004)10.5 current work

Literature

Ddry

N, Dwet

Mie CodeGrainger et al., 2004

(tabulate as )

Validating Radiative Forcing Sensitivity

ignore

Phase function coefficients for SIA(Dwet)Dmax

Dmin

Validating Radiative Forcing Sensitivity

Mie results for extinction at discrete mode diameters:

Radiative Forcing (forward calculation)

Chemical TransportModel

Mie Code

Aerosol concentrations

optical properties

Radiative Forcing Sensitivity

LIDORT Spurr, 2002

Jacobian calculation

GEOS-Chem AdjHenze et al., 2007

Mie Derivative

[SIA]*, [BC]*

Grainger et al., 2004

Radiative Forcing (forward calculation)

Chemical TransportModel

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 CodeLIDORT (Spurr 2002)

Jacobian calculation

GEOS-Chem Adj

Mie Derivative

[SIA]*, [BC]*

24 hr1 week

Radiative Forcing with GEOS-Chem

GEOS-Chem

N, Dwet

Mie CodeGrainger et al., 2004

[SIA], RH [BC]

Ddry

(external mixture)

Radiative Transfer CodeLIDORT (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 CodeGrainger et al., 2004

[SIA], [BC], RH, Ddry

Radiative Transfer CodeLIDORT (Spurr, 2002)

TOA upward SW flux

Forward model

Radiative Transfer Code

Mie Codederivate mode

GEOS-Chem Adj

Sensitivity calculation

[SIA]*, [BC]*

Weighting functions

Henze et al., 2007

24 hr

1 wk

Applying to CLE 2030 inventories

note: this takes about 10 seconds

Applying to MFR 2030 inventories