Rainfall in Western South America:

The “traditional El Niño”

versus

“Global ENSO”

C F Ropelewski and L Goddard

IRI

The Earth Institute, Columbia University

(With thanks to Yamina Silva, Instituto Geofisico Del Peru)

The 28th Climate Diagnostics and

Prediction Workshop

Reno NV, 20-23 October 2003

Traditional El Niño versus Global ENSO

El Niño – The maximum in mean annual cycle of sea surface temperature along the west coast of South America i.e. anomalies with respect to the annual mean

ENSO – Defined here as the positive displacement of the mean annual cycle of sea surface temperature in the equatorial Pacific i.e. anomalies wrt the mean annual cycle.

ENSO, El Niño and Climo

ENSO Composite Years

57 –58 (e.g. Jan 57 to Dec 58)

65 - 66

68 – 69

72 – 73

82 – 83

86 – 87

90 – 91

94 – 95

97 – 98

All Nino3 ,3.4, 1+2

Thanks to Vern Kousky

Event-to-Event Variability of SST Anomalies (El Niño)

SST Anomalies (1983-2003)

(Source CPC/NOAA)

Annual Cycle-Precipitation and Temperature(80.75S, 5.25W, New et al 1999)

Sea surface temperature

correlations

with FMA precipitation

in Peru

Correlations Nino1+2

-0.5 – -0.3-0.3 – 0.3 0.3 – 0.5 0.5 – 0.7 0.7 – 1.0

Thanks to YaminaSilva, InstitutoGeofisico Del Peru

Thanks to YaminaSilva, InstitutoGeofisico Del Peru

PrecipVsNINO12

Correlations Nino 3.4

-0.5 – -0.3-0.3 – 0.3 0.3 – 0.5 0.5 – 0.7 0.7 – 1.0

Thanks to YaminaSilva, InstitutoGeofisico Del Peru

Composite precipitation

in

tercile classes

for western South America

tropics

Occurrence Nino34

Occurrence Nino1+2

FMA Circ CompsMeridional

andVertical WindsMean

(1971-2000)

10S EQ10N

CompositeAnomalyNino1&210 warmest

Ranked Sea Surface Temperature for February-April NINO Areas

YEAR NINO1&2 NINO3.4 1950

53 8 57 5 58 9 3 1960

65 10 66 6 69 5 1970

72 6 73 8 1980

83 2 1 87 3 4 1990

92 4 2 93 7 10 95 7 98 1 (1) 2000

01 (n) 02 (n) Yellow – NINO1&2 only, RED – NINO3.4 Only

NINO1&2 – 4 Cases

NINO3.4 – 4 Cases

Both – 6 Cases

Ranked Sea Surface Temperature for February-April NINO Areas

YEAR NINO1&2 NINO3.4 1950

53 8 57 5 58 9 3 1960

65 10 66 6 69 5 1970

72 6 73 8 1980

83 2 1 87 3 4 1990

92 4 2 93 7 10 95 7 98 1 (1) 2000

01 (n) 02 (n) Yellow – NINO1&2 only, RED – NINO3.4 Only

NINO1&2 – 4 Cases

NINO3.4 – 4 Cases

Both – 6 Cases

NINO1&2WARMMARCH

1953

1957

1965

1972

NINO3.4OnlyMarch

1966

1969

1973

1995

1958

1983

1987

1992

1993

1998

March of years with both warm NINOP1&2 and NINO3.4

Summary• Rainfall in near equatorial regions of Ecuador

and Peru are sensitive to the “local” sst anomalies (NINO1&2 here) in FMA.

• Correlations i.e. teleconnections with central and western Pacific sst anomalies are weaker during the same season.

• Most large “local” FMA sst anomalies occur in conjunction with the larger scale ENSO phenomenon.

• There are some notable exceptions including: 1953, 1957, 1965, 1972 and most recently 2001 and 2002.

Nino 3.4

Thanks to Vern Kousky

Nino 1+2

Thanks to Vern Kousky

Correlations Nino 4.0

-0.5 – -0.3-0.3 – 0.3 0.3 – 0.5 0.5 – 0.7 0.7 – 1.0

Thanks to YaminaSilva, InstitutoGeofisico Del Peru

Correlations Nino 3

-0.5 – -0.3-0.3 – 0.3 0.3 – 0.5 0.5 – 0.7 0.7 – 1.0

Thanks to YaminaSilva, InstitutoGeofisico Del Peru

January N12PrecipVsNINO12

March N12PrecipVsNINO12

Thanks to YaminaSilva, InstitutoGeofisico Del Peru

February N12

Thanks to YaminaSilva, InstitutoGeofisico Del Peru

PrecipVsNINO12