El Niño (Spanish name for the male child), initially referred to a weak, warm current appearing annually around Christmas time along the coast of Ecuador and Peru and lasting only a few weeks to a month or more. Every three to seven years, an El Niño event may last for many months, having significant economic and atmospheric consequences worldwide. During the past forty years, ten of these major El Niño events have been recorded, the worst of which occurred in 1997-1998. Previous to this, the El Niño event in 1982-1983 was the strongest. Some of the El Niño events have persisted more than one year. .
El Niño Years.
1902-1903 1905-1906 1911-1912 1914-1915.
1918-1919 1923-1924 1925-1926 1930-1931.
1932-1933 1939-1940 1941-1942 1951-1952.
1953-1954 1957-1958 1965-1966 1969-1970.
1972-1973 1976-1977 1982-1983 1986-1987.
1991-1992 1994-1995 1997-1998.
Selected text from: CPC ENSO Main Page .
In the tropical Pacific, trade winds generally drive the surface waters westward. The surface water becomes progressively warmer going westward because of its longer exposure to solar heating. El Niño is observed when the easterly trade winds weaken, allowing warmer waters of the western Pacific to migrate eastward and eventually reach the South American Coast (shown in orange). The cool nutrient-rich sea water normally found along the coast of Peru is replaced by warmer water depleted of nutrients, resulting in a dramatic reduction in marine fish and plant life. .
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Animation by: Shao .
In contrast to El Niño, La Niña (female child) refers to an anomaly of unusually cold sea surface temperatures found in the eastern tropical Pacific. La Niña occurs roughly half as often as El Niño. .
La Niña Years.
1904-1905 1909-1910 1910-1911 1915-1916.
1917-1918 1924-1925 1928-1929 1938-1939.
1950-1951 1955-1956 1956-1957 1964-1965.
1970-1971 1971-1972 1973-1974 1975-1976.