El Fenómeno de El NiñoEl fenómeno ENSO (El Niño SouthernOscillation)

1. Surface flow may be directed westward at speeds of 25–75 cm/s;2. Current reverses at a depth of from 20 to 40 m;3. Eastward undercurrent extends to a depth of 400 meters with a transportof as much as 30 Sv = 30 × 106 m3/s;4. Core of maximum eastward velocity (0.50–1.50 m/s) rises from a depth of100 m at 140◦W to 40 m at 98◦W, then dips down;5. Undercurrent appears to be symmetrical about the equator and becomesmuch thinner and weaker at 2◦N and 2◦S.In essence, the Pacific Equatorial Undercurrent is a ribbon with dimensions of

El Niño/Southern Oscillation (ENSO) is the most important coupled ocean-atmosphere phenomenon to cause global climate

variability on interannual time scales. Here we attempt to monitor ENSO by basing the Multivariate ENSO Index (MEI) on

the six main observed variables over the tropical Pacific. Thesesix variables are: sea-level pressure (P), zonal (U) and meridional(V) components of the surface wind, sea surface temperature (S),surface air temperature (A), and total cloudiness fraction of the

sky (C). The MEI is computed separately for each of twelve sliding bi-monthly seasons (Dec/Jan, Jan/Feb,..., Nov/Dec). After

spatially filtering the individual fields into clusters (Wolter, 1987), the MEI is calculated as the first unrotated Principal Component (PC) of all six observed fields combined. In order to keep the MEI comparable, all seasonal values are standardized with respect to

each season and to the 1950-93 reference period. Negative values of the MEI represent the cold ENSO phase, a.k.a.La Niña, while positive MEI values represent the warm

ENSO phase (El Niño).

INDICE DE OSCILACION SUR

(TAHITI - DARWIN)