la ninña
What
is La Niña?
Recent
La Niña and El Niño events
La
Niña impact on the global climate
The
origin of the names, La Niña and El Niño
Selected
references and publications
What is La Niña?
La Niña is characterized by unusually cold ocean temperatures in the Equatorial Pacific, compared to El Niño, which is characterized by unusually warm ocean temperatures in the Equatorial Pacific.
La Nina (cold) conditions -
view of
Pacific water temperatures
Normal
Conditions
El Nino Conditions
Normal Equatorial Pacific
Ocean surface temperatures (December 1993) are shown in the middle
panel,
including cool water, called the 'cold tongue', in the Eastern Pacific
(in blue, on the right of the plot) and warm water in the Western
Pacific
(in red, on the left). Strong La Niña conditions during
December
1998 are shown in the top panel. The Eastern Pacific is cooler than
usual,
and the cool water extends farther westward than is usual (see the blue
color extending further to the left). Strong El Niño
conditions,
in December 1997, are shown on the bottom panel, with warm water (red)
extending all along the equator. El Niño and La
Niña are
opposite phases of the El Niño-Southern Oscillation (ENSO)
cycle,
with La Niña sometimes referred to as the cold phase of ENSO
and
El Niño as the warm phase of ENSO.
Recent
La Niña and El Niño events
Different
La Niña and El Niño events vary in strength
Mean
and anomalies of sea surface temperature from 1986 to present, showing
El Niño events 1986-1987, 1991-1992, 1993, 1994 and 1997 and
La
Niña events in 1985 and 1995.
In the left hand panel,
you see the sea surface temperature at the Equator in the Pacific Ocean
(Indonesia is towards the left, South America is towards the right).
Time
is increasing downwards from 1986 at the top of the plot, to the
present,
at the bottom of the plot. The first thing to note is the blue
"scallops"
on the right of the plot, in the eastern Pacific. These indicate the
cool
water typically observed in the Eastern Pacific (called the "cold
tongue").
Cold tongue temperatures vary seasonally, being warmest in the northern
hemisphere springtime and coolest in the northern hemisphere fall. The
red color on the left is the warm pool of water typically observed in
the
western Pacific Ocean. El Niño is an exaggeration of the
usual
seasonal
cycle.
During the El Niño
in 1986-1987, you can see the warm water (red) penetrating eastward in
the Spring of 1987. There is another El Niño in 1991-1992,
and
you
can see the warm water penetrating towards the east in the northern
hemisphere
spring of 1992. The 1997-1998 El Niño (at the bottom) is
unusually
strong.
El Niño and
La Niña years are easier to see in the anomalies on the
right
hand
panel. The anomalies show how much the sea surface temperature is
different
from the usual value for each month. Water temperatures significantly
warmer
than the norm are shown in red, and water temperatures cooler than the
norm are shown in blue. In the right-hand plot of sea surface
temperature
anomalies, it is very easy to see El Niño's, with water
warmer
than
usual (red) in the eastern Pacific, during in 1986-1987, 1991-1992,
1993,
1994 and 1997-1998. It is unusual for El Niños to occur in
such
rapid succession, as was the case during 1990-1994.
Notice the very cool
water (blue), in the Eastern Pacific, in 1988-1989, and the somewhat
less
cool water in 1995. These are La Niña events, which occur
after
some (but not all) El Niños. Typically, El Niño
occurs
more
frequently than La Niña.
La
Niña impact on the global climate
Global climate La
Niña impacts tend to be opposite those of El Niño
impacts.
In the tropics, ocean temperature variations in La Niña tend
to
be opposite those of El Niño.
At higher latitudes,
El Niño and La Niña are among a number of factors
that
influence
climate. However, the impacts of El Niño and La
Niña at
these
latitudes are most clearly seen in wintertime.
The
origin of the names, La Niña and El Niño
La
Niña is sometimes referred to as El Viejo
El Niño was
originally recognized by fisherman off the coast of South America as
the
appearance of unusually warm water in the Pacific ocean, occurring near
the beginning of the year. El Niño means The Little Boy or
Christ
child in Spanish. This name was used for the tendency of the phenomenon
to arrive around Christmas.
La Niña means
The Little Girl. La Niña is sometimes called El Viejo,
anti-El
Niño,
or simply "a cold event" or "a cold episode".
Selected references and publications
NOAA Reports to the Nation - El Niño and Climate Prediction