Agriculture Reference
In-Depth Information
CHAPTER THREE
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Almost all the studies performed during the past century have shown that
drought is not the result of a single cause. Instead, it is the result of many
factors varying in nature and scales. For this reason, researchers have been
focusing their studies on the components of the climate system to explain
a link between patterns (regional and global) of climatic variability and
drought.
Some drought patterns tend to recur frequently, particularly in the trop-
ics. One such pattern is the El Niño and Southern Oscillation (ENSO). This
chapter explains the main characteristics of the ENSO and its data forms,
and how this phenomenon is related to the occurrence of drought in the
world regions.
[28],
El
Niño
Originally, the name El Niño was coined in the late 1800s by fishermen
along the coast of Peru to refer to a seasonal invasion of south-flowing
warm currents of the ocean that displaced the north-flowing cold currents
in which they normally fished. The invasion of warm water disrupts both
the marine food chain and the economies of coastal communities that are
based on fishing and related industries. Because the phenomenon peaks
around the Christmas season, the fishermen who first observed it named
it “El Niño” (“the Christ Child”). In recent decades, scientists have rec-
ognized that El Niño is linked with other shifts in global weather patterns
(Bjerknes, 1969; Wyrtki, 1975; Alexander, 1992; Trenberth, 1995; Nichol-
son and Kim, 1997).
The recurring period of El Niño varies from two to seven years. The
intensity and duration of the event vary too and are hard to predict. Typi-
cally, the duration of El Niño ranges from 14 to 22 months, but it can also
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