Overview Total Irradiance SORCE/TIM observations and database variability components, models, comparisons Spectral Irradiance

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1 Comparison of Solar Irradiance Variability Models with SORCE Observations Judith Lean 1, Jerald Harder 2, Greg Kopp 2 1. Space Science Division, Naval Research Laboratory, Washington DC 2. LASP, University of Colorado, Boulder CO Overview Total Irradiance SORCE/TIM observations and database variability components, models, comparisons Spectral Irradiance spectral irradiance models comparison with SORCE/SIM GISS general circulation middle atmosphere model simulations SORCE STM, 5FEB08

2 SORCE/TIM Continues a 28-year Record of Total Solar Irradiance ACRIM PMOD Past Solar Activity sunspot cycle amplitudes have increased from the Maunder Minimum to the Modern Maximum! 5-min oscillation ~ 0.003%! 27-day solar rotation ~ 0.2%! 11-year solar cycle ~ 0.1%! longer-term variations not yet detectable do they occur? data: Fröhlich & Lean,AARev,

3 Modeling Sources of Solar Irradiance Variability - dark sunspots - bright faculae 17 OCT OCT JUN FEB 02 sunspots dominate faculae during solar rotation faculae dominate sunspots during 11-yr solar cycle I(t) = I quiet +!I spots +!I faculae

4 TSI Model from TIM Multiple Regression 17 OCT OCT 03 common TSI data TIM TIM Model PMOD Model Mean (Wm -2 ) Standard Deviation (Wm -2 ) Slope (Wm -2 yr -1 ) TIM model o matches shorter time scale changes better than model from PMOD composite (overall variance is larger in common epoch) o underestimates long-term change (due to limited dataset?)

5 Observed and Modeled Total Solar Irradiance TIM total irradiance is decreasing less rapidly than VIRGO or ACRIM during declining cycle 23

6 Radiative Processes in the Earth s Atmosphere Depend on Wavelength UV radiation (! < 315 nm) 20 Wm -2 ozone Sun near UV,VIS,IR Radiation (! > 315 nm) 1346 Wm -2 unit optical depth Stratosphere cloud cover

7 Solar Spectral Irradiance Variability Model UV radiation varies more than visible radiation because UV faculae are brighter UARS/ SOLSTICE SOLSPEC sunspot NRLSSI model: 1 nm bins ,000 nm daily since 1947 monthly since 1882 yearly since 1610 faculae 0.1 micron 1 micron 10 micron magnetic fields have different effects on radiation at different wavelengths Lean, 2000

8 Estimating Long-Term Solar Variability surface magnetic fields of opposite polarity transported by differential rotation, meridional flow, diffusion NRL Flux Transport Model Wang et al., 2003 sub-surface dynamo closed flux modulates irradiance open flux modulates cosmogenic isotopes Irradiance at Earth 1365 Wm % Galactic Cosmic Ray Flux at Earth Wm -2 Lean et al., 2005

9 NRL Solar Spectral Irradiance Model Users User Application David Rind NASA/GISS GCM simulations V. Ramaswamy NOAA/GFDL GCM simulations David Lary NASA/GSFC AutoChem Kunihiko Kodera MRI, Tskuba, Japan Strat.-climate model Don Wuebbles Univ. Illinois Strat. model Katja Matthes Freie Univ. Berlin SOLARIS model comparisons Wavelength Range Number of Bins ,000 nm 190 bins ,000 nm 18 bins nm 203 bins nm 171 bins nm 134 bins EUV ,000 nm 3780 bins Time Period Cadence monthly monthly daily monthly monthly daily

10 NRL Spectral Irradiance Variability Model is Available on the Web Atmospheric Chemistry Modeling and Assimilation TIM SIM nm bands nm nm bands.. 1 nm , nm nm nm 5,000-10, nm nm 10, ,000 5,000-10,000 nm nm nm 10, ,000 daily nm since nm daily monthly since since nm 203 bands daily since 1976

11 Comparison of NRL Spectral Irradiance Variability Model with SORCE/SIM 17 OCT OCT 03 Spectral Band (nm) SORCE Rotation 30 Oct 2003/ 17 Oct 2003 Model Rotation 30 Oct 2003/ 17 Oct 2003 Model Solar Cycle 1989/

12 A New UV/Vis/IR Spectral Irradiance Variability Model from SORCE Data Current Model reference (quiet Sun) spectrum from UARS/SOLSTICE and SOLSPEC New Model (from SORCE data) reference (quiet Sun) spectrum consistent with SIM and SOLSTICE wavelength-dependent sunspot and facular contrasts are consistent with rotational modulation measured by UARS SOLSTICE (! < 400 nm) from Unruh theoretical model (! > 400 nm) integral of sunspot blocking and facular brightening match the bolometric (total) values derived from the multiple regression of PMOD 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) from Unruh theoretical model (! > 1600 nm) integral of sunspot blocking and facular brightening match the bolometric (total) values derived from the multiple regression of TIM data - bolometric sunspot contrast 0.43

13 Spectral Irradiance Variability Model from SORCE Data: Details SORCE Data F(!,t) Model Inputs P s (t) P f (t) SOLSTICE B ( nm), SOLSTICE A ( nm) SIM UV ( nm), SIM VIS1 ( nm) SIM VIS2 ( nm), SIM IR ( nm) bolometric sunspot blocking calculated from USAF images faculae time series from composite Mg index (Viereck & SORCE) Model Formulation F m (!,t)=[a 0 (!)+ a 1 (!)(P f (t)-p fa )/P fa +a 2 (!)(P s (t)-p sa )/P sa ]F a (!)+F a (!) 1 nm grid (on 0.5 nm centers) from 115 to 1600 nm daily mean time series from April all time series smoothed twice with ±40-day square wave detrended by converting to fractional changes F d =(F(!,t)- F s (!,t))/ F a (!) etc multiple linear regression performed for detrended spectral irradiance time series at each! F d =a 0 (!)+ a 1 (!)P fd (t)+a 2 (!)P sd (t)

14 SORCE vs. Modeled Spectral Irradiance SORCE absolute spectral irradiance agrees with SOLSPEC and UARS (model) to within ~5% Real differences occur in regions dominated by UV spectral lines, and in near IR continuum

15 SORCE vs. Modeled Irradiance Variability SORCE Lean (2000) new model NOTE: model derived from detrended time series

16 SORCE vs.. Model Correlations Model of sunspot and facular influences explains significant short-term variance (> 60%) except at interfaces of individual optical trains within the SORCE instrument suite: SOLSTICE FUV: nm SOLSTICE MUV: nm SIM UV: nm SIM VIS1: nm SIM VIS2: nm SIM IR: nm

17 Wavelength-dependent solar irradiance variability produces height dependent atmospheric response SURFACE MIDDLE TROPOSPHERE LOWER STRATOSPHERE Temperature Anomaly (K) El Nino + La Nina El Chichon Pinatubo solar increase " warming CO 2 increase " warming volcanoes " cooling solar increase " warming CO 2 & CFC increase " cooling volcanoes " warming

18 Correlation Patterns: Temperature vs. Irradiance (observed, and simulated with GISS middle atmosphere GCM forced with monthly spectral irradiance variations ) SURFACE Multiple regression MIDDLE TROPOSPHERE Hadley cell LOWER STRATOSPHERE Ferrel cell B30TRoims1M23 B465trsuvoioTM53 solar solar, (no interactive ozone) ozone

19 Comparison of Solar Irradiance Variability Models with SORCE Observations: SUMMARY SORCE solar irradiance data are helping answer: how and why solar irradiance varies - total and spectra? what are the mechanisms and wavelength dependence of irradiance variability? are long-term changes occurring in addition to the 11-year cycle? how and why does climate respond to wavelength-dependent irradiance variations? Short-term solar Irradiance changes arise primarily from wavelength-dependent sunspot and facular sources increased uncertainties at interfaces of SORCE optical trains extant sunspot (Allen) and facular (Unruh) contrasts need some adjustments to better account for SORCE/SIM spectral variations Longer-term solar Irradiance changes are uncertain ongoing, continuous irradiance record is crucial for better understanding and improved historical reconstructions: SORCE! Glory!?? (TSIS demanifested from NPOESS) Solar-driven climate change occurs simultaneously with other natural and anthropogenic influences volcanic influences, internal modes (ENSO, QBO), greenhouse gases, aerosols surface and atmospheric temperatures respond to solar cycle with complex spatial patterns interactive ozone is crucial for modeling responses to solar forcing throughout the` atmosphere