Solar Spectral Irradiance:Solar Spectral Irradiance:Users, Applications, ModelsUsers, Applications, Models

Judith LeanNaval Research Laboratory, Washington DC

MotivationMotivation- atmospheric, surface and ocean transmission, reflection, scattering and absorption are all wavelength dependent

- solar radiative forcing is spatially and altitudinally dependent

Users and ApplicationsUsers and Applications- inputs for model simulations of present and past climate and atmospheric processes and variability

Spectral Irradiance Variability ModelSpectral Irradiance Variability Model- wavelength-dependent sunspot and facular influences

SORCE Irradiance ObservationsSORCE Irradiance Observations- SIM and SOLSTICE TIM (thanks to Jerry H. for sending SIM data)

- comparison with models

Global Heat FlowsGlobal Heat Flows

Kiehl and Trenberth, 1997

5880 K 4 K

SUN (255 K)+GHG (33 K)=288 K

Incoming Solar RadiationIncoming Solar Radiation

cycle 21max

cycle 22max

341.5 Wm-2

= 1366/4

SOHO: 1996

ACRIMSAT: 1999

SORCE: 2003

StratosphereStratosphere

unit

optical

depth

UV radiation( < 315 nm)

20 Wm-2Sun

Solar Radiative Processes Depend onSolar Radiative Processes Depend on

Geography Geography andand AltitudeAltitude

near UV,VIS,IR Radiation

( > 315 nm)1346 Wm-2

ozone

cloud cover

Spectral Irradiance Users & ApplicationsSpectral Irradiance Users & Applications

1975-2000

monthly

1882-2000

monthly

1976-2005

daily

1976-2004

monthly

1880-2005

monthly

Time Period

Cadence

117-100,000 nm

190 bins

David RindNASA/GISS

GCM simulations

120-735 nm

134 bins

Don WuebblesUniv. Illinois

Strat. model

116-735 nm

171 bins

Kunihiko KoderaMRI, Tskuba, Japan

Strat.-climate model

121-850 nm

203 bins

David LaryNASA/GSFC

AutoChem

202-100,000 nm

18 bins

V. RamaswamyNOAA/GFDL

GCM simulations

Wavelength Range

Number of Bins

User

Application

Climate ModelsClimate Models

Hansen et al., JGR, 2002

117-100,000 nm190 bands

Lary, DJ, Halogens and the chemistry of the free

troposphere, Atmospheric Chemistry And Physics,

5, 227-237, 2005.

Atmospheric ChemistryAtmospheric ChemistryModeling andModeling andAssimilation:Assimilation:AutoChemAutoChemCDACentralCDACentral

121-859 nm203 bands

Solar Irradiance Variability Models: Solar Irradiance Variability Models: TotalTotal

- faculae

- sunspots

Fröhlich & Lean, Astron. Astrophys. Rev., 2004

0.1 micron 1 micron 10 micron

magnetic fields have different effectson radiation at different wavelengths

sunspot

faculae

UV radiation varies more than visibleradiation because UV faculae are brighter

Solar Spectral Irradiance Variability ModelSolar Spectral Irradiance Variability Model

Lean, 2000; Lean et al., 2005

UARS/SOLSTICE

SOLSPEC

model: 1 nm bins 120-100,000 nm daily since 1947 monthly since 1882 yearly since 1610

Reconstructed Historical Solar IrradianceReconstructed Historical Solar Irradiance

0.075%

0.2%

Flux transport simulations suggest that

accumulated total magnetic flux produces a

smaller facular contribution to secular irradiance

change than in previous reconstructions

Since the Maunder Minimum: total irradiance increase = 1.1 Wm-2

climate forcing = 0.2 Wm-2

surface temperature increase = 0.1-0.2oC ( = 0.5-1oC per Wm-2)

Wang et al., ApJ, 2005

Solar Spectral Irradiance

Lean et al., Sol. Phys., 2005

Solar Irradiance Validation: Solar Irradiance Validation: TotalTotal

17 O

CT

03

30 O

CT

03

Lean et al., Solar Phys., 2005

-0.069(0.005%)

0.96341.003650.4791365.95Model

-0.191(0.014%)

0.99671.004230.5771366.73SARR

-0.261(0.019%)

0.98291.003750.5821366.09ACRIM

-0.134(0.010%)

0.99641.003510.5731365.76PMOD

-0.182(0.013%)

110.5791360.98TIM

Slope(W m-2 per

year)

Correlationwith TIM

Ratio toTIM

StandardDeviation(W m-2)

MeanValue

(W m-2)

TSIRecord

Irradiance variability model derived

from multiple regression of sunspot

and facular indices with the PMOD

composite underestimates the TSI

variance observed by SORCE/TIM

Solar SpectralSolar SpectralIrradiance Irradiance Validation:Validation:

UV/Vis/IRUV/Vis/IR

17 OCT 03 30 OCT 03

1.000250.99820.99801000-1600

1.00040.99750.9979700-1000

1.00080.99670.9965400-700

1.0020.99560.9959315-400

1.0130.99930.9990200-300

ModelSolarCycle

1989/1986

ModelRotation

30 Oct 2003/17 Oct 2003

SORCERotation

30 Oct 2003/17 Oct 2003

SpectralBand(nm)

//

TSI Model from TIM Multiple RegressionTSI Model from TIM Multiple Regression

Variance is increased in irradiance

variability model derived from multiple

regression of sunspot and facular

indices with TIM data, relative to

model derived from PMOD composite

0.448

0.385

0.463Standard

Deviation

(Wm-2)

-0.125

-0.135

-0.150Slope

(Wm-2yr-1)

1360.9

1365.84

1360.9Mean

(Wm-2)

TIM Model

PMOD Model

TIM

common TSI data2003.17-2006

Comparison of PMOD and TIM ModelsComparison of PMOD and TIM Models

New UV/Vis/IR Spectral IrradianceNew UV/Vis/IR Spectral IrradianceVariability Variability ModelModel

integral of sunspot blocking andfacular brightening match thebolometric (total) values derivedfrom the multiple regression of TIMdata

- bolometric sunspot contrast 0.43

integral of sunspot blocking andfacular brightening match thebolometric (total) values derivedfrom the multiple regression ofPMOD composite data

- bolometric sunspot contrast 0.36

wavelength-dependent sunspot and

facular contrasts are consistent

with rotational modulation

measured by SIM and SOLSTICE

( < 1600 nm) and from Unruh

theoretical model ( > 1600 nm)

wavelength-dependent sunspot and

facular contrasts are consistent

with rotational modulation

measured by UARS SOLSTICE

( < 400 nm) and from Unruh

theoretical model ( > 400 nm)

reference (quiet Sun) spectrum

consistent with SIM and SOLSTICE

reference (quiet Sun) spectrum from

UARS/SOLSTICE and SOLSPEC

New Model

(from SORCE data)

Current Model

SORCE vs. Modeled VariabilitySORCE vs. Modeled VariabilitySORCE

Lean (2000)new model

SORCE vs. Modeled Spectral IrradianceSORCE vs. Modeled Spectral Irradiance

SORCE solar irradiance spectra are helpingSORCE solar irradiance spectra are helpinganswer the Sun-climate questions:answer the Sun-climate questions:

- how and why does climate respond to wavelength-dependentirradiance variations?

- are solar-induced surface temperature changes limited to 0.1-0.2oC?

- what are the roles of land, atmosphere and oceans in directsurface heating?

- what are the indirect effects of radiative and dynamical verticalatmospheric couplings?

- does solar forcing induce mode amplification (ENSO, QBO),stochastic resonance, frequency modulation, triggering alteredstability states (AO, AAO)?

- mechanisms for significant hydrological cycle responses?

- how and why does solar irradiance vary?

- what are the mechanisms of irradiance variability?

- are long-term changes occurring in addition to the 11-year cycle?

Construction of a Solar Spectral IrradianceConstruction of a Solar Spectral IrradianceVariability Model from SORCE dataVariability Model from SORCE data

SOLSTICE B V5 (115.5 -179.5 nm)

SOLSTICE A V5 (180.5 – 309.5 nm

SIM V9 UV (201.5 – 306.5 nm)

SIM V9 VIS1 (310.5 – 955.5 nm)

SIM V9 VIS2 (338.5 – 1071.5 nm)

SIM V9 IR (849.5 – 1664.5 nm)

1 nm grid (on 0.5 nm centers) from 115 to 1600 nm

daily mean time series from April 2004 – 2006 F( ,t)

bolometric sunspot and faculae time series from TIM TSI model, Ps(t) Pf(t)All time series smoothed twice with ±40-day squarewave

- detrended by converting to fractional changes

Fd=(F( ,t)- Fs( ,t))/ Fa( )

Multiple linear regression performed for detrended spectral irradiance time

series at each Fd=a0( )+ a1( ) Pfd(t)+a2 ( ) Psd(t)

Irradiance model calculated from proxies byFm( ,t)=(a0( )+ a1( ) (Pf(t)-Pfa)/Pfa+a2 ( ) (Ps(t)-Psa)/Psa)

Fa( ,t)+Fa( ,t)