El Nino and La Nina
El Nino
• El Nino refers to the irregular warming in
the sea surface temperatures from the
coasts of Peru and Ecuador to the
equatorial central Pacific.
• El Nino is a disruption of the ocean-
atmosphere system in the tropical Pacific
ocean.
El Nino
• It has important consequences for weather
around the globe.
• This phenomenon is not totally predictable
but on average occurs once every four
years.
• It usually lasts for about 18 months after it
begins.
El Nino effects
• El Nino causes increased rainfall in the
South and unseasonably warm weather in
the North.
Why does El Nino happen?
• The Trade winds slow down in the
Central and Western Pacific.
• The colder water that the trade winds
usually bring up, stays lower in the ocean.
• This makes the sea surface temperatures
stay high.
• El Nino Years: 1902, 1905, 1911, 1914,
1918, 1923, 1925, 1930, 1932, 1939,
1941, 1951, 1953, 1957, 1965, 1969,
1972, 1976, 1982, 1986, 1991, 1994,
1997, 2002, 2006
Normal year versus El Nino year
El Nino year versus Normal year
La Nina
• La Niña is characterized by unusually cold
ocean temperatures in the Equatorial Pacific.
• La Niña tends to bring nearly opposite
effects of El Niño to the United States —
wetter and cooler than normal conditions
across the north and dryer and warmer than
normal conditions across much of the south.
• La Niña (Cold) Phases: 1904, 1908, 1910,
1916, 1924, 1928, 1938, 1950, 1955, 1964,
1970, 1973, 1975, 1988, 1998, 2000
Why does La Nina happen?
• The Trade winds strengthen in the
Central and Western Pacific.
• The trade winds bring up more cold water.
• This makes the sea surface temperatures
stay cold.
La Nina versus Normal year year
When can we notice this?
• The impacts of El Niño and La Niña at
these latitudes are most clearly seen in
wintertime.
Why El Nino?
• El Niño was originally recognized by
fisherman off the coast of South America
because of unusually warm water in the
Pacific ocean, occurring near the
beginning of the year.
– Less fish
• 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.
Why La Nina?
• 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".
El Nino vs La Nina