El Niño and theSouthern Oscillation

(“ENSO”)

A quick look

“Normal” SST

Walker circulation

ps(hPa)

Anomalous ps scaled by s.d.

Correlations (×10) of fluctuations in annual mean sea level pressure with those at Darwin. The magnitude of the correlation exceeds 0.4 in the shaded regions. (After Trenberth and Shea, 1987.)

Cx0 ,x p x 0,tp x,t

p 2x 0,t p 2x,t

1880 1890 1900 1910 1920-40

-30

-20

-10

0

10

20

30

40

soi

1920 1930 1940 1950 1960-40

-30

-20

-10

0

10

20

30

40

soi

1960 1970 1980 1990 2000-40

-30

-20

-10

0

10

20

30

soi

soi

Southern Oscillation Index 1880-2000

SOI 10 SLPTahiti SLPDarwin

1880 1890 1900 1910 1920-40

-30

-20

-10

0

10

20

30

40

soi

1920 1930 1940 1950 1960-40

-30

-20

-10

0

10

20

30

40

soi

1960 1970 1980 1990 2000-40

-30

-20

-10

0

10

20

30

soi

soi

Southern Oscillation Index 1880-2000

SOI 10 SLPTahiti SLPDarwin

“Normal” SST

Walker circulation

“Normal” SST

Sea surface temperature anomalies (C)

0 – 10S, 80 – 90W

1950 1955 1960 1965 1970 1975-4

-3

-2

-1

0

1

2

3

4

SO

I, S

ST

ano

mal

y (K

)

1975 1980 1985 1990 1995 2000-4

-3

-2

-1

0

1

2

3

4S

OI,

SS

T a

nom

aly

(K)

SST anomalies (Nino 1+2) vs SOI

SOI

SST

Annual rainfall (in percentiles) in a selection of regions. Black bars coincide with "El Niño" years.

cold

warm

cold

warm

Correlations (×10) of fluctuations in annual mean sea level pressure with those at Darwin. The magnitude of the correlation exceeds 0.4 in the shaded regions. (After Trenberth and Shea, 1987.)

Cx0 ,x p x 0,tp x,t

p 2x 0,t p 2x,t

El Nino impacts in U.S. winter

recent behavior in and over the equatorial Pacific

Current SST anomalies 2011 May 9