Atmosphere-Ocean coupling (only Pacific)

1. The Role of the sun in Atmosphere-Ocean coupling by Indrani Roy Atmosphere-Ocean coupling (only Pacific)

2. Summary • Overview of Solar influence on climate in a form of flow chart. • Description: Three major variability; viz. solar, QBO and ENSO with oval outlines; major circulations, responsible for modulating the effect shown by non-rectangular parallelograms. • Pathways of signals marked by ‘A’ – ‘Z’; direction of change in behaviour by ‘+’ (for increase) or ‘-’ (for decrease). • Subscripts indicate steps of same process; Superscripts same effect but different forcing - radiative or dynamical. Main Points: • Holistic Representation: An overview how atmosphere and ocean is influenced by solar variability. • How it is disturbed during last half of 20th century. • Why true quantification of solar signal is so difficult.

3. Few points on solar climate relationship • The Sun is principal source of energy in the earth- causes day/night and seasons- reasons to believe solar variability can influence climate. • 11 year solar variability is important one as it can be used for prediction purpose. • In terms of energy output only .1 % change from max to min years of 11 year cycle – too negligible to influence climate. • Why regionally different? Some region significant and also depends on time period.Unless any mechanism to support it can be coincidence. Holistic representation of solar 11 year cycle on climate

4. Outline • Background • Troposphere - Stratosphere Coupling Role of Sun Role of Sun+QBO • Atmosphere - Ocean Coupling Role of Sun+QBO+ENSO Role of Sun+QBO+ENSO+Climate change • Summary

5. Background: Climatology - SLP [ http://www.ux1.eiu.edu/~jpstimac/1400/circulation.html]

6. Climatology: SST [ http://www.atmos.albany.edu./deas/atmclasses/atm305/climomaps.html ]

7. General Circulation [http://www.metoffice.gov.uk/education/secondary/teachers/atmosphere.html#main] • As SST is always warmer in tropics, general circulation plays role to • transport heat from tropics to pole. • Three North South cells [Hadley cell, Polar cell (both thermally driven) • and Ferrel cell] and jet in between mainly responsible. • MidlattitudeFerrel cell via major eddies transport heat poleward.

8. Background: Stratosphere-troposphere coupling CharneyDrazen Criteria: stationary waves propagate only if: Winter Northern Hemisphere Westerlies in mid to high latitudes 1. Background flow is W ly and not too strong In mid-latitudes orography and land-sea temperature contrasts generate long Rossby waves in troposphere. and 2. Long waves (wave no. 1 or 2)

9. Schematic Representation Zero wind line Meridional temperature gradient sets up westerly jet in winter stratosphere Planetary–scale waves (PW) propagate upwards under W ly flow in winter hemisphere PWs grow and break: decelerating westerlies and warming pole. • PW propagation is sensitive to: • Strength of westerlies – Solar influence • Location of zero wind line- QBO influence (CIRA climatology, Fleming et al., 1990)

10. Role of zero wind line : QBO influence Mechanism: Holton-Tan Effect: QBO Ely - warmer pole 1. During E-ly QBO, zero-wind line moves to subtropics of the winter hemisphere 2. It narrows width of planetary wave-guide • Planetary waves • redirected polewards 4. When such wave events with large amplitude break or dissipate they warm polar stratosphere. zonal mean wind differences [Baldwin et al., 2001]

11. Multiple Regression Analysis SSN 11

12. Atmosphere only Sun via Lower stratosphere (C-F) Warming tropical lower stratosphere (-) C D Δ Hadley cell ΔSolar (Decadal) E (-) Δ Ferrel cell F Pole-ward shift & weakening of STJ C: Haigh (1996), Gray and Frame (2010) D, E, F: Haigh (2005, 2006), Brönnimann (2006)

13. Observational (C): Gray and Frame (2010) Observational (D,E,F): Haigh Model (D,E,F): Haigh

14. Atmosphere only: Sun via Lower stratosphere and mid-latitude of Pacific (C-H) Cloud free Midlatitude of Pacific (+) ΔTrade wind (DJF) D1 C1 Warming tropical lower stratosphere C H D (-) Δ Hadley cell ΔSolar (Decadal) E Influence AL and PH (DJF) Δ Ferrel cell (-) G F Pole-ward shift & weakening of STJ G: Christoforou and Hameed (1997); H, G: Our result (Regression) C1, D1: Meehl et al (2008)

15. Aleutian Low(AL) and Pacific High (PH) Christoforou and Hameed, 1997 (G) Result Solar (H,G) : Regression (DJF)

16. ‘Bottom up’ Mechanism: Meehl et al , 2008 (C1, D1) • ‘Bottom up’ suggests : • More solar radiation through cloud free mid-latitude of pacific in active solar years. • Increased latent heat flux, increased moisture convergence –strengthen trade wind.

17. Atmosphere only: Sun and Polar vortex (A, I-K) ΔSolar (Decadal) ΔPolar Vortex (+) A A, I : Usual mechanism following thermal wind balance I J, K : Baldwin (2005); Our result (Regression) Intensification of PJ (+) J Δ AAO (+) Δ AO K

18. Annular Modes pattern similar (J,K)- Baldwin and Dunkerton (2005) NAM at 1000 hPa and 10 hPa for Nov-Apr ,1958-2000

19. Regression : Solar signal in polar modes (J,K) SSN(JJA)1856-2004 SSN (Annually) 1856-1957 • Both AO and AAO signal is seen during 1856-1957 • AAO signal is seen in JJA even for whole 150 yr period (1856-2004) • Using different TSI, the result is similar for solar cycle variability

20. Atmosphere only: Sun, polar vortex and lower stratosphere B: Kodera and Kuroda (2002) B (B.D.Circulation)

21. Solar influence: Polar vortex and lower stratosphere (B) Solar UV at 205 nm increases ~6% from solar min to solar max More ozone heating in upper stratosphere alters temperature and wind structure Solar heating anomalies also change the strength of polar stratospheric jet (U) This influences the path of upward propagating planetary waves which deposit their zonal momentum on the poleward side of the jet. (Fig: Kodera and Kuroda, 2002)

22. Stratosphere-Troposphere Coupling: Sun+QBO(A-M) Δ QBO (Quasi-biannual Oscillation) L (-) M (-) L, M: our result (Regression, Roy & Haigh, 2011)

23. Sun, QBO and Polar temperature in north pole Composites of time height development of NAM [Baldwin and Dunkerton, 2001] [Labitzke and van Loon, 1992] E ly/ Sol Min Warm W ly/ Sol Max Warm W ly/Sol Min Cold E ly/ Sol Max Cold • W-ly QBO/ Solar min coldest • E-ly QBO/ Solar max also cold Perturbation in polar stratosphere can affect troposphere for next few months

24. Sun, QBO and Atmosphere Regression of SLP with Solar*QBO(50 hPa): L,M -veAO -veAAO Active sun-westerly QBO and less active sun-easterly QBO both trigger negative AO and AAO features

25. Ocean Coupling (Pacific) Ocean Global ocean Conveyor belt: Connect mid-latitude of Pacific to tropics (+) Thermocline shifting Q O1 ΔENSO (inter-annual) (-) (+) Shallow MOC (+) N. Pacific warming P [http://science.nasa.gov/headlines/y2004/05mar_arctic.htm] Walker circulation Cold Event of ENSO [http://www.cpc.noaa.gov/products/analysis_monitoring/socycle/meanrain.shtml] [http://www.cpc.noaa.gov/products]

26. Niño SST and Thermocline slope interconnected [http://www.cpc.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf] Volume transport convergence and SST averaged over eastern tropical Pacific [Zhang et. al. 2006]

27. Atmosphere-Ocean (Pacific) Coupling: Sun+QBO+ENSO(A-S) Atmosphere Ocean Cloud free Midlatitude of Pacific N (+) Thermocline shifting (+) ΔTrade wind (DJF) C1 D1 Warming tropical lower stratosphere H C C D Q O1 Δ Hadley cell (-) (B.D. Circulation) Δ Walker cell ΔENSO (inter-annual) (-) (+) B Shallow MOC O2 ΔSolar (Decadal) (+) (+) ΔPolar Vortex (B.D. Circulation) A R E (-) Influence AL and PH (DJF) Δ Ferrel cell N. Pacific warming G1 (+) P F G2 I Pole-ward shift & weakening of STJ S Intensification of PJ N, O2: Usual ENSO mechanism S: Carvalho et al., 2005 L (+) J (-) Δ AAO R: Camp and Tung (2007), Thompson and Baldwin (2001) + (-) (+) Δ AO M K ΔQBO (Quasi-biannual) G2: Our result (Regression)

28. ENSO and JET : Carvalho et al., 2005 (S) Zonal wind (200 hPa) Negative AAO phase Positive AAO phase Negative-Positive • Cold ENSO are linked with dominant positive AAO and vice versa • AAO phases are allied with latitudinal migration of STJ and intensity • of mid-latitude polar jet

29. Polar vortex and ENSO (R) : Thompson and Baldwin (2001) (Weak-strong vortex) Regression : Mid-latitude warming (G2)

30. Nature of ENSO was different before 1950s (and after 1997) • Strong decrease in strength of shallow meridional overturning circulation (MOC) around tropical Pacific after 1950s • Modest intensification since 1998 • Also true for Walker and Hadley circulation; more in Walker. (McPhaden and Zhang,2004;Vecchi and Soden 2007) (1856-1957) & (1998-2007) (1958-1997) SunSpot Number SunSpot Number ENSO (DJF) ENSO (DJF) Could change in ocean and atmosphere circulation due to climate change during that period have modified the solar- ENSO behaviour?

31. Atmosphere-Ocean Coupling: Sun+QBO+ENSO+Climatechange (A-Z) Atmosphere Ocean Cloud free Midlatitude of Pacific N (+) Thermocline shifting (+) ΔTrade wind (DJF) (-) C1 D1 X Climate Change (2nd half of 20th century) Warming tropical lower stratosphere H C D V2 W Q O1 T (-) Δ Hadley cell (-) U V1 (-) (B.D. Circulation) Δ Walker cell (-) ΔENSO (inter-annual) (-) (+) B Shallow MOC (+) O2 ΔSolar (Decadal) (+) (+) ΔPolar Vortex (B.D. Circulation) A R E Z (-) Y Influence AL and PH (DJF) Δ Ferrel cell N. Pacific warming G1 (+) G2 P F I Pole-ward shift & weakening of STJ S Intensification of PJ U, T, W : (McPhaden and Zhang,2004; Vecchi, et al. 2007) L (+) J (-) Δ AAO V1, V2 : Usual ENSO mechanism + (-) (+) Δ AO V1 : Our result (Regress., Roy-Haigh 2012) M K ΔQBO (Quasi-biannual) X, Z : Our result (Regression, do)

32. Solar Signal was different during 1958-1997 (X,Z,V1) 1958-1997 (DJF) 1856-1957(DJF) We are interested • No solar signal is seen around ITCZ of eastern Pacific during later period • Signal around AL weakened

33. Solar Signal on Tropical Pacific SST during 1958-1997(V1) Regression (SSN) for SST White et al. (1997) • Warming in tropical E. Pacific after 1950s, follows White et al, (1997) • But .. • No signal when ENSO is included in regression. • Also suggests White et al (1997) may not be true in earlier period.

34. Solar signal during 1958-1997 is also different in polar modes SSN (1958-1997) SSN (1856-1957) • Pathways R and S may be potential route to influence polar modes. • Using different Total Solar Irradiance (TSI), the result is similar.

35. Atmosphere-Ocean coupling (only Pacific) • Next: In holistic representation include • NAO and Indian summer monsoon • Atlantic and Indian Ocean

36. Summary • Discussed how sun is affecting troposphere. • The effect is different in poles, if QBO is included. • How ocean and atmosphere are connected. • Active sun can influence SST in tropical Pacific though overwhelmed by strong influence of ENSO at LS period. Main Points: • Proposed an overview how atmosphere and ocean might be affected by solar variability. • How the effect is disturbed during last half of 20th century. • Why true quantification of solar signal is so difficult.

37. Interested in Details Roy, I., 2013, ‘The role of the sun in atmosphere-ocean coupling’, International Journal of Climatology, doi:10.1002/joc.3713.

38. Atmosphere-Ocean coupling (only Pacific)

39. The role of the sun in Atmosphere-Ocean Coupling Indrani Roy