Pcf. Van Der Vaart et al., The Pacific cold tongue and the ENSO mode: A unified theory within the Zebiak-Cane model, J ATMOS SCI, 57(7), 2000, pp. 967-988
The equatorial tropical Pacific climate system is a delicate coupled system
in which winds driven by gradients of sea surface temperature (SST) within
the basin interact with the ocean circulation to maintain SST gradients. T
his results in a time mean state having a strong zonal temperature contrast
along the equator with an eastern cold tongue and a western warm pool. By
the same coupled processes, interannual variability, known as the El Nino-S
outhern Oscillation (ENSO), is present in the Pacific. This variability can
be attributed to an oscillatory coupled mode, the ENSO mode, in the equato
rial ocean-atmosphere system. Using a Zebiak-Cane-type intermediate coupled
model. the coexistence of an eastern cold tongue in the annual mean state
and ENSO in the Pacific climate system is investigated. The ENSO mode arise
s as a robust oscillatory mode on a coupled mean state and becomes unstable
if the cold tongue of the mean,rate is sufficiently strong. The origin of
this mode, its propagation mechanism, its sensitivity to parameters, and it
s relation to the spatial structure of the annual mean state are considered
.