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10 SCF Folio
Understanding the ENSO phenomenon
and its implications
Ask anyone about what he/she thinks El Niño place and something must be done to address its
is and the usual answers would be—a possible consequences.
severe drought or a long hot summer or a
dry spell followed by heavy rains. While all of these are
indeed associated with El Niño, they are, however,
merely the effects or impacts of this phenomenon. What
it really is lies somewhere in the Pacific.
Feeling the heat
Although the physical occurrence of El Niño (and La
Niña) takes place in the Pacific, its effects are felt in other
parts of the world, similar to a ripple effect in a big pond.
This is due to the so-called southern oscillation (SO)
What it basically is…
El Niño is a condition that takes place in the Central and
Eastern Equatorial Pacific (CEEP) Ocean, when the sea
surface temperature (SST) becomes unusually warmer
than the normal temperature. This condition can prevail
for more than a year, thus adversely affecting the
economy in both local and global scale.
The sea or ocean surface usually registers a certain
normal temperature. Any departure from this normal
level is considered an anomaly. If the temperature rises
from normal, it is called a positive anomaly. This
condition is associated with El Niño. Conversely, if the
temperature drops from normal, it is called a negative
anomaly and is more popularly related to La Niña. Either
way, any change in the temperature, just like in the
human body, indicates that something unusual is taking
which refers to a “see-saw” in atmospheric pressure
between the western (represented by Darwin in
Australia) and eastern Pacific (represented by the island
of Tahiti).
These variations in the atmosphere in the Pacific,
combined with changes in the SST as discussed earlier,
are responsible for bringing about abnormal climatic
events. The interaction between sea and atmosphere
variations refers to the El Niño Southern Oscillation
(ENSO) and potentially influences extreme climate
events in the world (El Niño refers to the ocean or sea
component of ENSO while the SO refers to the
atmospheric component).
El Niño and La Niña are basically flip sides (warm
and cold phases, respectively) of the ENSO and as such,
do not take place simultaneously in one area/region.
However, in terms of
teleconnection or the links of
El Niño
El Niño (EN) is Spanish for “The Christ Child,” a name given by Peruvian fishermen to the
phenomenon that they usually observed during the period near Christmas time when the water in
climate over great distances, if
the eastern part of the Pacific
experiences an unusual ocean
the Pacific Ocean off the coast of Peru would become unusually warm. Every two to nine years, for
warming and low atmospheric
unexplained reason, trade winds in the Pacific region, which drive the surface warm waters of the
pressure (characteristics of the
tropics to the west Pacific, weaken. As a result, these warm waters of the western Pacific drift
eastward, resulting in the occurrence of El Niño in the eastern part of the Pacific.
warm phase or El Niño), then the
western part of the Pacific will
Southern oscillation
Southern oscilllation (SO) is an east-west balancing movement of air masses between the eastern
likely experience the opposite
effect, characterized by cooler
Pacific and the Indo-Australian areas. It is measured as the difference between the overlying
ocean and high atmospheric
atmospheric pressures at Darwin (northern Australia) and Tahiti (south-central Pacific). This term
pressure.
was coined by the British scientist named Sir Gilbert Walker during the 1920s when he observed
that when the atmospheric pressure rises in the east, the waters of the eastern Pacific are unusually
cold, and when the atmospheric pressure drops in the eastern Pacific, the waters in this part of the
Pacific are unusually warm. The opposite effects are observed in the western Pacific.
The implications
The effects of ENSO on climate
variability all over the globe