Atmosphere-Ocean coupling (only Pacific)

The Role of the sun in Atmosphere-Ocean coupling by Indrani Roy

Summary

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.

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.

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

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

Background: Climatology - SLP

[ http://www.ux1.eiu.edu/~jpstimac/1400/circulation.html]

Climatology: SST

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

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.• Midlattitude Ferrel cell via major eddies transport heat poleward.

Background: Stratosphere-troposphere coupling

1. Background flow is W ly

and not too strong

and 2. Long waves (wave no. 1 or 2)

Westerlies in mid to high latitudes

Winter Northern Hemisphere

In mid-latitudes orography and land-sea temperature contrasts generate long

Rossby waves in troposphere.

Charney Drazen Criteria: stationary waves propagate

only if:

Schematic Representation

(CIRA climatology, Fleming et al., 1990)

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:1. Strength of westerlies – Solar influence

2. Location of zero wind line- QBO influence

Zero wind line

Role of zero wind line : QBO influenceMechanism:

1. During E-ly QBO, zero-wind line moves to subtropics of the winter hemisphere

2. It narrows width of planetary wave-guide

3. Planetary waves redirected polewards

4. When such wave events with large amplitude

break or dissipate they warm polar stratosphere.

zonal mean wind differences

Holton-Tan Effect:

QBO Ely - warmer pole

[Baldwin et al., 2001]

11

Multiple Regression Analysis

SSN

Pole-ward shift & weakening of STJ

Sun via Lower stratosphere (C-F)

(-)

(-)

Δ Solar(Decadal)

Δ Ferrel cell

C

E

F

Atmosphere only

Δ Hadley cell

Warming tropical lower stratosphere

D

D, E, F: Haigh (2005, 2006), Brönnimann (2006)

C: Haigh (1996), Gray and Frame (2010)

Observational (D,E,F): Haigh Model (D,E,F): Haigh

Observational (C): Gray and Frame (2010)

ΔTrade wind(DJF)

Pole-ward shift & weakening of STJ

Atmosphere only: Sun via Lower stratosphere and mid-latitude of Pacific (C-H)

(-)

(-) Influence AL and PH (DJF)

Δ Solar(Decadal)

Δ Ferrel cell

E

F

H

(+)

G

Δ Hadley cell

Warming tropical lower stratosphere

D

G: Christoforou and Hameed (1997); H, G: Our result (Regression)

C

Cloud free Midlatitude of Pacific D

1

C1

C1, D1: Meehl et al (2008)

Aleutian Low(AL) and Pacific High (PH)Christoforou and Hameed, 1997 (G)

Result Solar (H,G) : Regression (DJF)

‘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.

Intensification of PJ

Δ Polar Vortex

Δ Solar(Decadal)

Δ AAO

Δ AO (+)

A

J

K

Atmosphere only: Sun and Polar vortex (A, I-K)

I

(+)

(+)

A, I : Usual mechanism following thermal wind balance

J, K : Baldwin (2005); Our result (Regression)

NAM at 1000 hPa and 10 hPa for Nov-Apr ,1958-2000

Annular Modes pattern similar (J,K)- Baldwin and Dunkerton (2005)

Regression : Solar signal in polar modes (J,K)

• 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

SSN(JJA)1856-2004SSN (Annually) 1856-1957

Atmosphere only: Sun, polar vortex and lower stratosphere

B: Kodera and Kuroda (2002)B (B.D.Circulation)

(Fig: Kodera and Kuroda, 2002)

Solar influence: Polar vortex and lower stratosphere (B)

Solar UV at 205 nm increases ~6% from solar min to solar max

This influences the path of upward propagating planetary

waves which deposit their zonal momentum on the poleward

side of the jet.

More ozone heating in upper stratosphere

alters temperature and wind structure

Solar heating anomalies also change the strength

of polar stratospheric jet (U)

Stratosphere-Troposphere Coupling: Sun+QBO (A-M)

L, M: our result (Regression, Roy & Haigh, 2011)

L (-)

M (-)

Δ QBO(Quasi-biannual Oscillation)

Composites of time height development of NAM

[Baldwin and Dunkerton, 2001]

Perturbation in polar stratosphere can affect troposphere for next few months

Sun, QBO and Polar temperature in north pole

[Labitzke and van Loon, 1992]

• W-ly QBO/ Solar min coldest• E-ly QBO/ Solar max also cold

E ly/ Sol MinWarm

W ly/ Sol MaxWarm

E ly/ Sol MaxCold

W ly/Sol MinCold

Sun, QBO and Atmosphere

Active sun-westerly QBO and less active sun-easterly QBO both trigger negative AO and AAO features

Regression of SLP with Solar*QBO(50 hPa): L,M

-ve AO

-ve AAO

(-)

Ocean

Shallow MOC

Thermocline shifting

(+)

(+)

Q

Δ ENSO (inter-annual)

O1

N. Pacific warming

(+)P

Ocean Coupling (Pacific) Global ocean Conveyor belt: Connect mid-latitude of Pacific to tropics

Walker circulation Cold Event of ENSO

[http://science.nasa.gov/headlines/y2004/05mar_arctic.htm]

[http://www.cpc.noaa.gov/products/analysis_monitoring/socycle/meanrain.shtml]

[http://www.cpc.noaa.gov/products]

Niño SST and Thermocline slope interconnected

Volume transport convergence and SST averaged over eastern tropical Pacific

[http://www.cpc.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf]

[Zhang et. al. 2006]

Δ Walker cell

ΔTrade wind

(DJF)

Pole-ward shift & weakening of STJ

(+)

(-)

(-)

Atmosphere Ocean

(-)

(-)

N

S

Shallow MOC

Thermocline shifting

(+)

(+)

Influence AL and PH (DJF)

Intensification of PJ

Δ Polar Vortex

Q

(B.D. Circulation)

Δ Solar(Decadal)

Δ QBO (Quasi-biannual)

Δ ENSO (inter-annual)

Δ AAO

Δ AO (+)(-)

(B.D. Circulation)

Δ Ferrel cell

A

C

E

F

+

HO1

O2

R

J

K

L

M

N. Pacific warming (+)

(+)

G1PG2

Atmosphere-Ocean (Pacific) Coupling: Sun+QBO+ENSO (A-S)

B

I

Δ Hadley cell

Warming tropical lower stratosphere

D

(+)

(+)

N, O2: Usual ENSO mechanism

S: Carvalho et al., 2005

R: Camp and Tung (2007), Thompson and Baldwin (2001)

G2: Our result (Regression)

C

Cloud free Midlatitude of Pacific

D1

C1

ENSO and JET : Carvalho et al., 2005 (S)

• 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

Negative AAO phase

Positive AAO phase

Negative-Positive

Zonal wind (200 hPa)

Polar vortex and ENSO (R) : Thompson and Baldwin (2001)

(Weak-strong vortex)

Regression : Mid-latitude warming (G2)

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)

Nature of ENSO was different before 1950s (and after 1997)

Could change in ocean and atmosphere circulation due to climate change during that period have modified the solar- ENSO behaviour?

SunS

pot N

umbe

r

SunS

pot N

umbe

r

(1958-1997)(1856-1957) & (1998-2007)

ENSO (DJF) ENSO (DJF)

Δ Walker cell

ΔTrade wind

(DJF)

Pole-ward shift & weakening of STJ

Climate Change(2nd half of 20th century)

(+)

(-)

(-)

(-)

Atmosphere Ocean

(-)

(-)

(-)

N

S

Shallow MOC

(-)

Thermocline shifting

(+)

(+) (-)

(+)

Influence AL and PH (DJF)

Intensification of PJ

Δ Polar Vortex

QW

(B.D. Circulation)

X

Δ Solar(Decadal)

Δ QBO (Quasi-biannual)

Δ ENSO (inter-annual)

Δ AAO

Δ AO (+)(-)

(B.D. Circulation)

Δ Ferrel cell

A

C

E

F

+

HO1

O2

R

J

K

L

M

U

T

V1

N. Pacific warming (+)

V2

(+)

G1PG2

Z

Atmosphere-Ocean Coupling: Sun+QBO+ENSO+Climate change (A-Z)

B

I

Δ Hadley cell

Warming tropical lower stratosphere

D

(+)

(+)

U, T, W : (McPhaden and Zhang,2004; Vecchi, et al. 2007)

Y

V1, V2 : Usual ENSO mechanismV1 : Our result (Regress., Roy-Haigh 2012)X, Z : Our result (Regression, do)

Cloud free Midlatitude of Pacific

D1

C1

1958-1997 (DJF)1856-1957(DJF)

Solar Signal was different during 1958-1997 (X,Z,V1)

• No solar signal is seen around ITCZ of eastern Pacific during later period

• Signal around AL weakened

We are interested

Solar Signal on Tropical Pacific SST during 1958-1997(V1)

But ..• No signal when ENSO is included in regression.• Also suggests White et al (1997) may not be true in earlier period.

Regression (SSN) for SST White et al. (1997)

• Warming in tropical E. Pacific after 1950s, follows White et al, (1997)

Solar signal during 1958-1997 is also different in polar modes

• Pathways R and S may be potential route to influence polar modes.

• Using different Total Solar Irradiance (TSI), the result is similar.

SSN (1856-1957) SSN (1958-1997)

Atmosphere-Ocean coupling (only Pacific)

Next: In holistic representation include

NAO and Indian summer monsoon Atlantic and Indian Ocean

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.

Interested in Details

Roy, I., 2013, ‘The role of the sun in atmosphere-ocean coupling’, International

Journal of Climatology, doi:10.1002/joc.3713.

Atmosphere-Ocean coupling (only Pacific)

The role of the sun in Atmosphere-Ocean Coupling

Indrani Roy