The Influence of Solar Variability on the Atmosphere and Ocean Dynamics

1. The Influence of Solar Variability on the Atmosphere and Ocean Dynamics Speaker：Pei-Yu Chueh Adviser：Yu-Heng Tseng Date：2010/10/12

2. Review

3. Observation-Solar variability The amplitude of the solar cycle is relatively small, about 0.2 Wm−2 globally averaged (Lean 2005), and the observed global SST response of about 0.1°C would require more than 0.5 Wm−2 (White 1998), there has always been a question regarding how this small solar signal could be amplified to produce a measurable response.

4. Observation-Solar signals • Atmosphere • Ocean bathythermograph [van Loon et al., 2000] [White et al., 1997]

5. Review-The influence of solar forcing • Small-amplitude variations in solar radiation that occur during the approximately 11-yr solar cycle [the decadal solar oscillation (DSO)] may produce significant responses in the troposphere and ocean. Specifically for the Indo-Pacific region. • [Haigh 1996, 2001, 2003; Lean and Rind 2001; Rind 2002; Lean et al. 2005; van Loon and Labitzke 1998; van Loon and Shea 1999, 2000; Gleisner and Thejll 2003; van Loon et al. 2004; Crooks and Gray 2005; Wang et al. 2005; Bhattacharyya and Narasimha 2005; Lim et al. 2006; White et al. 1997, 1998; Bond et al. 2001; Weng 2005]

6. Review-The influence of solar forcing • solar induced percentage ozone changes between solar max and min Annual Mean (%) Solar maximum → more UV radiation → more ozone [Haigh, 1994]

7. Review-The influence of solar forcing ERA40 (1979-2001) +1.75K +0.5K [Crooks and Gray, 2005]

8. Review-The influence of solar forcing [Meehl, 2008]

9. The Walker cell and the QBO in solar peak years • Walker cell: 120°E-70°W and 2°N-2°S • QBO (Quasi-Biennial oscillation) definition: according to the November mean Singapore wind at the 50‐hPa level. If the wind is westerly (W), the year is categorized as a W year. [van Loon and Meehl, 2008; Kuroda and Yamazaki, 2010]

10. Comparison with cold extremes (CE) in the Southern Oscillation • Cold extremes • Solar peak years SLP Trades are stronger. SST [van Loon and Meehl, 2008]

11. Comparison with cold extremes (CE) in the Southern Oscillation • Cold extremes • Solar peak years Vertical zonal wind [van Loon and Meehl, 2008]

12. Review-Mechanism The top-down stratospheric ozone mechanism • Increased solar • increased ozone heating/Increased ozone amount • modified temperature and zonal wind • altered wave propagation • changed equator to pole energy transport and circulation • enhanced tropical precipitation [Haigh, 1996; Shindell et al., 1999; Balachandran et al., 1999]

13. Review-Mechanism The bottom-up coupled air-sea mechanism Increased solar over cloud-free regions of the subtropics translates into greater evaporation, and moisture convergence and precipitation in the ITCZ and SPCZ (and south Asian monsoon), stronger trades, and cooler SSTs in eastern equatorial Pacific. [Meehl et al., 2003; Van Loon et al., 2007]

14. Could the two mechanisms add together to boost the climate response to solar forcing? Observed Bottom-up only Top-down only Both bottom-up and top-down [Meehl et al., 2009; Rind et al., 2008]

15. Motivation • Is the quasi-decadal oscillation (QDO) near 11-year period in global patterns of SST and SLP internal or external? • What are the influences of solar forcing on the atmosphere and ocean? Also, how these small variations affect our climate system? What ‘s the importance of solar forcing? • If we add the solar forcing in our model, could we find near 11-year period or another periods? Could we see the responses of solar forcingwhich are observed in previous data? Do these phenomena exist in our model output?

16. Objectives • Use model output data to investigate the role of 11-year solar forcing and the relationship between ENSO and solar forcing. • Use model experiments in reproducing the observed signals and to verify the mechanisms of solar forcing. • Solar forcing may affect the ocean heat storage. Try to quantify the magnitude of ocean heat content.

17. NAO-North Atlantic Oscillation [Bachmann, 2007]

18. Role of ozone in the solar cycle modulation of the North Atlantic Oscillation Winter-mean NAO index (DJF) [Kuroda, 2008]

19. Mechanism-Influence of the 11-Year Solar Cycle UV radiation Mesosphere Stratopause Stratosphere Tropopause Troposphere Direct influence on temperature Change of meridional temperature gradient SAO Influence on ozone Circulation changes (wind, waves, meridional BD circulation) QBO Change of Walker circulation Indirect influence, Difficult to measure Change of Hadley cell Increased energy input at surface in cloud free area Greater evaporation and moisture convergence (stronger trades) • [Matthes, 2005]

20. COSMOS = Community Earth system modeling system

21. Review-The influence of solar forcing In the atmosphere The Aleutian low moved westward and the Pacific subtropical high moved northwardduring solar maxima for the period 1900–94. [Christoforou and Hameed 1997] Variations in UV and solar-induced changes in ozone may have an effect on radiative forcing but additionally may affect climate through a dynamical response to solar heating of the lower stratosphere. [Haigh 2002] Solar did have impact on both the tropospheric and stratospheric meridional circulations. [Matthes et al. 2004, 2006]

22. Review-The influence of solar forcing In the ocean There is a cold event–like pattern during decadal periods of high solar forcing. [Mann et al. 2005] The decadal solar oscillation at its peaks strengthens the major convergence zones in the tropical Pacific during northern winter. [van Loon et al. 2007] Precipitation changes have also been reported, in particular increased precipitation in July and August in the tropical western Pacific, and the various monsoon regions: South Asian, west African, and North America. [Kodera, 2004; van Loon et al., 2004, 2007; Bhattacharya and Narasimha, 2005; Kodera and Shibata, 2006]

23. Review-Model Cubasch et al . (1997) suggested a possible solar contribution to the mid-20th century warming and a solar contribution of 40% of the observed global warming over the last 30 years. Stott et al .(2002), suggests that the GCM simulations may underestimate solar influence by up to a factor of three. One potential factor is the spectral composition of the solar irradiance variations and the resultant modulation of stratospheric ozone (Haigh 1994). Models in general are unable to simulate the necessary stratospheric ozone response, as they produce maximum ozone change in the mid stratosphere, instead of in the upper and lower stratosphere as observed. [e.g., Shindell et al., 1999; Tourpali et al., 2003; Egorova et al., 2004; Sekiyama et al., 2006]

24. Review-Model Haigh (1999) use a general-circulation model (GCM) to investigate the impact of the 11-year solar-activity cycle on the climate of the lower atmosphere. Solar forcing is represented by changes in both incident irradiance and stratospheric ozone concentrations. The GCM results suggest that the precise response of the atmosphere depends on the magnitude and distribution of the ozone changes. As the latitude-height structure of solar-induced ozone changes over the 11-year cycle are not yet well established, the general circulation models are able to produce some of the observed patterns of response to solar activity but generally underestimate the magnitude. [Haigh 2002]

25. Review-Model Lee(2009) use the Goddard Institute for Space Studies (GISS) Model to investigate tropical circulation. The model includes fully interactive atmospheric chemistry. The model experiments conditions: a doubly amplified solar forcing and the present-day and preindustrial greenhouse gases and aerosol conditions, with the mixed layer or fully coupled dynamic ocean model. With present-day greenhouse gas and aerosol conditions, theascending branch of the Hadley cell is enhanced near the equator, and the ITCZ is shifted northward in response to solar forcing during the boreal winter. Enhancement of the meridionally averaged vertical velocity over the western Pacific indicates strengthening of the Walker circulation in response to solar forcing in both solstice seasons.

26. Thank you!

27. Review-Mechanism • The variations in stratospheric ozone in response to solar variability. • Solar irradiance • UV • O3 • Stratosphere • Troposphere warming • Heating ocean [Haigh, 1996; Shindell et al., 1999; Balachandran et al., 1999]

28. Review-The influence of solar forcing SSU/MSU4 (1979-2003) +0.9K [Courtesy of Bill Randel, 2005]

29. Motivation(delete) • The quasi-decadal oscillation (QDO) near 11-year period was one of the principal signals observed in global patterns of sea surface temperature (SST) and sea level pressure (SLP) during the 20th century. • Observations have shown that the 11-year cycle of solar forcing may have some influences on climate system, in both the atmosphere and ocean. • However, the amplitude of solar cycle is relatively small, about 0.2 Wm-2. Therefore, we are interested in how these small variations affect our climate system. • If solar cycle is important, we could add this forcing in our models in the future to reproduce the observed signals more accurate.