1. 1 Pedagogical Review on Solar Cycles King-Fai Li Caltech GPS, YL Yung Group Jan 17, 2007

2. 2 Outline ► What are solar cycles? ► How are they related to climate? ► Our group ’ s efforts

3. 3 What are solar cycles? ► First observed in the time series of sunspot number

4. 4 Solar and Heliospheric Observatory (SOHO) ► Michelson Doppler Imager (MDI)   Ni I 6768 Å solar absorption line from the photosphere. ► Extreme ultraviolet Imaging Telescope (EIT)   171, 195, 284, and 304 Å, corresponding to light produced by highly ionized Fe-XI/X, XII, XV, and He-II;   Corona emissions

5. 5 MDI

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8. 8 Babcock Model 27-day differential surface rotation

9. 9 ► Total Spectral Irradiances Direct Observations  ~0.1% change in the 11-yr solar cycle

10. 10 Direct Observations ► F10.7 cm radio flux Blue: 90-day average

11. 11 ► Lyman-a line (1215 Å) Direct Observations  ~72% change in the 11-yr solar cycle

12. 12 ► Mg-II core-to-wing index (2800 Å) ► Active and passive sunspot projected areas Direct Observations (More … )

13. 13 How are they related to climate? Y L Yung ’ s Talk in CUHK, 2004

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16. 16 How much is due to the solar cycle effect?

17. 17 Empirical Data in Ozone Columns

18. 18 Solar Cycles and Climate ► ► Corti et al. (1999): External perturbation changes only the occurrence frequency of the natural modes due to the non-linearity of the system. ► ► QBO and Annular Modes are two examples of natural modes.

19. 19 Our group ’ s effort ► Solar cycle – Northern/Southern Annular Modes interactions from NCEP Reanalysis data; ► Solar cycle – QBO interactions from THIN AIR model; ► Solar cycles on atmospheric chemical species from observations over Table Mountain + Caltech/JPL photochemical Model ► Variability of Fraunhofer structures in the spectra (~3080 Å) observed over Table Mountain.

20. 20 Fraunhofer lines Measured on ground

21. 21 Fraunhofer lines

22. 22 Limb Spectra from Table Mountain 2005/6/13 2005/9/23 OH absorption lines We have discovered some time-varying asymmetry between east and west limb Fraunhofer structures!

23. 23 Summary ► What are solar cycles? ► How are they related to climate? ► Our group ’ s efforts  To distinguish between natural variabilities and anthropogenic effects on climate  To analysis the asymmetry between Fraunhofer structures at the solar limbs

24. 24 References ► ► Babcock, H.W., The Topology of the Sun's Magnetic Field and the 22-YEAR Cycle, Astrophys. J., 133, 572-587, 1961 ► ► Camp, C. D., M. S. Roulston, and Y. L. Yung, Temporal and Spatial Patterns of the Interannual Variability of Total Ozone in the Tropics, J. Geophys. Res., 108(D20), 4643, 2003. ► ► Corti, S., F. Molteni, and T. N. Palmer, Signature of recent climate change in frequencies of natural atmospheric circulation regimes, Nature, 398(6730), 799-802, 1999. ► Pap, J. M., Periodicities of Solar Irradiance and Solar Activity Indices, I, Solar Physics, 129, 165-189,1990. ► ► Rind, D., The Sun's Role in Climate Variations, Science, 296, 673 (2002).