Multidecadal Modulation of ENSO teleconnection with Europe

J. López-Parages (1) (2) , B. Rodríguez-Fonseca (1) (2), Dietmar Dommenget (3), and Claudia Frauen (4)

(1) Departmento de Física de la Tierra, Astronomía y Astrofísica I: Geofísica y Meteorología, Universidad Complutense de Madrid, Madrid, España. (2) Instituto de Geociencias (CSIC-UCM), Madrid, Spain. (3) School of Matematical Sciences, Monash University, Melbourne, Australia. (4) CERFACS, Toulousse, France.

http://tropa.fis.ucm.es/web/

ENSO European climate

Consistent and statistically significant ENSO signal (Fraedrich and Müller, 1992;

Moron and Gouirand, 2002; Moron and Plaut, 2003 ; Brönnimann et al. 2006)

1.1. Motivation and state of the art: Europe-ENSO link

Feb.

Mar.

SLP: Difference between warm and cold ENSO composite maps

(Moron and Gouirand, 2002)

• El Niño (Niña) impact tends to be accompanied by a negative (positive) NAO-like pattern

• Late winter and early spring is the more appropriate season to detect the ENSO signal

(Brönnimann et al. 2007 and paper therein)

ENSO signal over the Euro-Atlantic sector much more stronger after the 1970’s

(Greatbatch et al. 2004).

ENSO European climate

1.2. Motivation and state of the art: Europe-ENSO nonstationary link

P1: 1958-1977 P2: 1978-1997 DJF

Other studies: Mariotti (2002), Knippertz et al. 2003, Mathieu et al. 2004, Zanchettin

et al. 2008, Brönnimann et al., 2007 ...

95% significance Monte-Carlo test

21 y. moving window correlations PC1-Niño3.4

Interannual PC1 is only

correlated with El Niño under

negative AMO phases.

1910-1930 1930-1950 1950-1970 1970-1990

2.1. Observational results: EL NIÑO Influence

r~=0.8

(López-Parages & Rodríguez-Fonseca, GRL, 2012)

2.2. Sensitivity experiments with ACCESS Model

P: Clim_1950-2010 +

(Cold North Atl. & Warm tropical Pac.)

N: Clim_1950-2010 -

(Warm North Atl. & Cold tropical Pac.)

These patterns represents the

non-linear spatial structure of

ENSO in an optimal way

(Dommenget et al. 2013)

A low resolution version (3.75º x 2.5º) of the ACCESS-slab model has been used (Bi et al. 2013)

• Atmosphere: Met Office Unified Model

• Ocean: AGCM is coupled to a simple slab ocean model (with flux correction)

Set of sensitivity experiments:

'UUU 1)

NP UorU

2) ''

EPCP UorU

...,,, ''''

EPNEPPEPNEPP UUUUUUUU

2.3. Sensitivity experiments with ACCESS Model : +EP

'

EPPP UUU '

EPNN UUU

2.3. Sensitivity experiments with ACCESS Model : +EP

'

EPPP UUU '

EPNN UUU

Stronger rotational

response in P

2.3. Sensitivity experiments with ACCESS Model : + EP

'

EPPP UUU '

EPNP UUU

NP UU

Stronger rotational

response in P

Positive KS anomalies reflect

regions with a reinforced

waveguide

(Hoskins & Ambrizzi, 1993)

Changes in Rossby

waveguides

2.3. Sensitivity experiments with ACCESS Model : + EP

'

EPPP UUU '

EPNP UUU

NP UU

NP UU

2.4. +EP: mechanism

…. the seasonal cycle of the jetstreams determines to a large extent the behaviour of the Rossby wavetrains propagation reaching the North Atlantic-European region in response to the different oceanic forcings... (García-Serrano. PhD Thesis, 2010)

1) Rotational Flow

NP UU

2.5. Sensitivity experiments with ACCESS Model : - CP

'

CPPP UUU '

CPNN UUU

2.5. Sensitivity experiments with ACCESS Model : - CP

'

CPPP UUU '

CPNN UUU

NP UU

Stronger inter-basin

link in P

2.6. -CP: mechanism

NP UU

2) Divergent Flow

•The leading iEMedR mode in FMA is significantly related to El Niño in a nonstationary

way. An observational hint of multidecadal modulation of the El Niño influence is found.

• This changing link evolve in phase with AMO along the 20th century.

• Sentitivity experiments (ACCESS Model), for which idealized ENSO SST patterns are

superimposed over different SST mean states, confirm a nonstationary impact over the

NAES.

• For eastern Niños, the non-stationary impact is mainly explained by changes in the

downstream propagation of the tropical disturbances from the Pacific to the North

Atlantic. These feature could be modulated by significant changes in the climatological

zonal mean flow.

• For central Niñas, the non-stationary impact seems to occurs in association with a

changing Walker-Hadley circulation, which modifies the Azores high pressure

system.

• To deeper investigate the internal nature of this non-stationary teleconnection, control

simulations of CMIP5 models have been analyzed (see poster 3.2).

3. Conclusions

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