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Solar Variability and Climate: From Mechanisms to Models

Solar Variability and Climate: From Mechanisms to Models. Terry Nathan Atmospheric Science Program University of California, Davis. OUTLINE SUN-CLIMATE CONNECTIONS CHALLENGES 11-YEAR SOLAR FORCING KEY CIRCULATION COMPONENTS OF CLIMATE SYSTEM SOLAR VARIABILITY, OZONE AND WAVES

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Solar Variability and Climate: From Mechanisms to Models

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  1. Solar Variability and Climate:From Mechanisms to Models Terry NathanAtmospheric Science ProgramUniversity of California, Davis OUTLINE SUN-CLIMATE CONNECTIONS CHALLENGES 11-YEAR SOLAR FORCING KEY CIRCULATION COMPONENTS OF CLIMATE SYSTEM SOLAR VARIABILITY, OZONE AND WAVES PATHWAYS AND INTERFACES FUTURE ILWS 2009, Brazil

  2. SUN-CLIMATE CONNECTIONS

  3. Global Average Radiative Forcing (RF) Estimates LOSULevel of Scientific Understanding IPCC 4th Assessment Report 2007

  4. Paleo Sun–Climate Synopsis …when solar activity is high…. increased temperature & moisture SW Alaska Sheng et al., 2003 drought Western US Cookl et al., 2001 warming North Atlantic Bond et al., 2000 stronger monsoon Wangxiang cave Zhang et al., 2008 high rainfall Oman Neff et al., 2001 drought Equatorial East Africa Verschuren et al., 2000 weakened upwelling and trade winds (warmer SSTs) Cariaco Basin Black et al., 1999 warming Beijing Tan et al., 2004 Mayan drought Cariaco Basin Hodell et al., 2001 Haug et al., 2003 streamflow Parana River Mauas et al., 2008. tree-rings Chile Roig et al., 2001 Nordemann et al. warming Tasmania Hill et al., 2007 Courtesy J. Lean significant local changes do not imply global changes of equal magnitude

  5. Natural and Anthropogenic Change in Earth’s Atmosphere 2km LOWER TROPOSPHERE 5km MID TROPOSPHERE 19km LOWER STRAT Courtesy of Judith Lean

  6. 11-YEAR SOLAR FORCING • - Total solar irradiance (TSI) changes • Solar spectral irradiance (SSI) changes • - 11-year solar cycle modulation in high energy particles (e.g., solar protons, galactic cosmic rays)

  7. CHALLENGES • - TSI Variations <0.1% • - Identification of pathways that communicate and amplify solar variability throughout the atmosphere and oceans • Address discrepancies between models and observations

  8. Total Solar Irradiance (TSI) changes <0.1% 1600 1700 1800 1900 2000YEAR From Lean, Ann. Rev of Astron. & Astrophys., 1997

  9. Solar Spectral Irradiance (SSI) changes Variations in SSI over the Solar Cycle 8% 4% 20% 0.5% From Lean, Ann. Rev of Astron. & Astrophys., 1997 Stratospheric Ozone Heating Rates Adapted from Strobel (1978) JGR

  10. KEY CIRCULATION COMPONENTS OF CLIMATE SYSTEM • Quasi-biennial oscillation (QBO) • Hadley circulation, subtropical jets… • - Stratospheric polar vortex • Brewer-Dobson circulation • Planetary waves • ……..

  11. Quasi-biennial Oscillation (QBO) Time–height plot of equatorial zonal wind (u) in m/s between about 20 and 35 km altitude above sea level over a ten-year period. Positive values denote westerly winds and thecontour line is at 0 m/s. After Holton et al

  12. Hadley Circulation, Subtropical Jets …

  13. Stratospheric Polar Vortex Pole 660

  14. Brewer-Dobson Circulation

  15. Planetary Waves Stratospheric Polar Vortex Brewer-Dobson Vertically Propagating Planetary Waves WAVE DRAG

  16. SOLAR VARIABILITY, OZONE AND WAVES

  17. Connection betweenSSI and PWD Variations in Solar Spectral Irradiance PWD Longitudinal Variations in Ozone Heating “NEW” Zonal-MeanVariations in Ozone Heating “TRADITIONAL” Planetary Wave Drag(propagation / attenuation) Why is PWD so important? Zonal-Mean Flow Residual Mean Meridional Circulation, PWD Vertically Propagating Wave EP-Flux Divergence F = Fyj + Fzk momentum flux heat flux

  18. WKB Solution for EP-Flux Divergence (1-D) SSI-Modified Vertical Wavenumber (Refractive Index) SSI-Modified Planetary Wave Drag Zonal-Mean Flow Equation Nonlinear function of SSI

  19. Ozone-Modified Downward Control Residual Vertical Velocity“Downward Control” To what extent is the divergence of Eliassen-Palm flux (i.e., PWD) affected by the solar-modulated, planetary wave induced ozone heating? Adapted from Holton 2004

  20. PATHWAYS AND INTERFACES

  21. Variations in SSI and TSI - Solar Proton Events – Cosmic Rays Impacts on Upper Atmospheric Chemistry and DynamicsDirect RF of the Lower Atmosphere Tropical Upwelling Downwelling Polar Vortex Quasi-biennial OscillationQBO Middle Atmosphere OZONE OZONE Vertically PropagatingPlanetary WavesPWD Vertically PropagatingTropical Waves WD 450 latitude HADLEY clouds clouds clouds clouds Surface Troposphere EQUATOR POLE

  22. FUTURE

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