Atmosphere-Ocean coupling (only Pacific)
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Transcript of Atmosphere-Ocean coupling (only Pacific)
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