Modern day research and reanalysis techniques have managed to find at least 26 El Niño events since 1900, with the 1982–83, 1997––16 events among the strongest on record. Around 1525, when Francisco Pizarro made landfall in Peru, he noted rainfall in the deserts, the first written record of the impacts of El Niño. Scientists have also found chemical signatures of warmer sea surface temperatures and increased rainfall caused by El Niño in coral specimens that are around 13,000 years old. For example, it is thought that El Niño affected the Moche in modern-day Peru. It is believed that El Niño has occurred for thousands of years. Loop of warming sea surface temperature (SST) anomalies in the Tropical Pacific The low-level surface trade winds, which normally blow from east to west along the equator, either weaken or start blowing from the other direction.
This warming causes a shift in the atmospheric circulation with rainfall becoming reduced over Indonesia, India and northern Australia, while rainfall and tropical cyclone formation increases over the tropical Pacific Ocean. However, over time the term has evolved and now refers to the warm and negative phase of the El Niño–Southern Oscillation and is the warming of the ocean surface or above-average sea surface temperatures in the central and eastern tropical Pacific Ocean. Originally, the term El Niño applied to an annual weak warm ocean current that ran southwards along the coast of Peru and Ecuador at about Christmas time. The original phrase, El Niño de Navidad, arose centuries ago, when Peruvian fishermen named the weather phenomenon after the newborn Christ. In this phase of the Oscillation, the pool of warm water in the Pacific near South America is often at its warmest about Christmas. ĭeveloping countries that depend on their own agriculture and fishing, particularly those bordering the Pacific Ocean, are usually most affected. The ENSO cycle, including both El Niño and La Niña, causes global changes in temperature and rainfall. The cool phase of ENSO is Spanish: La Niña, lit.'The Girl', with SSTs in the eastern Pacific below average, and air pressure high in the eastern Pacific and low in the western Pacific. During the development of El Niño, rainfall develops between September–November. El Niño phases are known to last close to four years however, records demonstrate that the cycles have lasted between two and seven years. The ENSO is the cycle of warm and cold sea surface temperature (SST) of the tropical central and eastern Pacific Ocean.Įl Niño is accompanied by high air pressure in the western Pacific and low air pressure in the eastern Pacific. 'The Boy') is the warm phase of the El Niño–Southern Oscillation (ENSO) and is associated with a band of warm ocean water that develops in the central and east-central equatorial Pacific (approximately between the International Date Line and 120°W), including the area off the Pacific coast of South America. America means upwelled water is warm and nutrient poor.Įl Niño ( / ɛ l ˈ n iː n j oʊ/ el NEEN-yoh, Spanish: lit. In strong El Niños the deeper thermocline off S.
El Niño conditions: warm water and atmospheric convection move eastwards.
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