1. 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
PATHWAYS AND INTERFACES
FUTURE
ILWS 2009, Brazil

2. SUN-CLIMATE CONNECTIONS

3. Global Average Radiative Forcing (RF) Estimates
LOSU Level 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
Mayan drought Cariaco Basin
Hodell et al., 2001
Haug et al., 2003
weakened upwelling and trade winds (warmer SSTs)
Cariaco Basin
Black et al., 1999
warming Beijing
Tan et al., 2004
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 5

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%
YEAR
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 the contour 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. Stratospheric Polar Vortex Vertically Propagating Planetary Waves
Brewer-Dobson
Vertically Propagating Planetary Waves
WAVE DRAG

16. SOLAR VARIABILITY, OZONE AND WAVES

17. Connection between SSI and PWD
Variations in Solar Spectral Irradiance
PWD
Zonal-Mean Variations in Ozone Heating
“TRADITIONAL”
Longitudinal Variations in Ozone Heating
“NEW”
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 Dynamics Direct RF of the Lower Atmosphere
Tropical Upwelling
Downwelling
Quasi-biennial Oscillation QBO
Polar Vortex
Middle Atmosphere
OZONE
OZONE
Vertically Propagating Planetary Waves PWD
Vertically Propagating Tropical Waves WD
450 latitude
clouds
HADLEY
clouds
clouds
clouds
Surface
Troposphere
EQUATOR
POLE

22. FUTURE