El Nino (the Christ Child) is the warming of the Eastern Pacific that occurs at intervals between two and 10 years. It can last for up to two years. Originally El Nino referred to a warm current that appeared off the coast of Peru, but the scientific community now know that it is part of a much larger system.
1. The Walker Circulation.
![Picture](/uploads/9/8/4/6/98460802/published/walker.jpg?1488019528)
The Walker Circulation is the east to west circulation that occurs in low latitudes (nearer the Equator). Near to South America, winds blow off shore which causes the upwelling of colder, nutrient rich waters. (This is good for nutrient cycling and the usual migratory patterns of some species- plankton and fish stocks). The winds blow across the Pacific, pushing warm surface waters to the west, meaning that the average sea surface temperature is over 28C which causes an area of low pressure and high rainfall. At the coast in South America, Sea Surface Temps are lower, and we see high air pressure, because of the atmospheric oscillation, meaning that the air sinks, so clouds don't develop and conditions are dry.
2. El Nino
During El Nino episodes, the usual Walker Circulation. Water temperatures in the eastern Pacific rise as warm water from the western Pacific flows into the East Pacific. During ENSO events, sea surface temperatures over 28C extend much further across the Pacific. Low pressure develops over the eastern Pacific, and high pressure over the West consequently heavy rainfall occurs over coastal South America, whereas Indonesia and the Western Pacific experience warm dry conditions. These events can cause extreme weather events which may be disastrous.
3. La Nina
Typically, a La Niña is preceded by a build-up of cooler than normal subsurface waters in the tropical Pacific. Eastward-moving atmospheric and oceanic waves help bring the cold water to the surface through a complex series of events, still being studied. In time, the easterly trade winds strengthen, cold upwelling off Peru and Ecuador intensifies, and sea-surface temperatures (SSTs) drop below normal. During the 1988-89 La Niña, SSTs fell to as much as 4°C below normal. Both La Niña and El Niño tend to peak during the Northern Hemisphere winter.
What is the difference between El Nino and La Nina?
Both terms refer to large-scale changes in sea-surface temperature across the central and eastern tropical Pacific. Usually, sea-surface readings off South America’s west coast range from about 15°C to 21°C, while they exceed 25°C in the ‘warm pool’ located in the central and western Pacific. This warm pool expands to cover the tropics during El Niño, but shrinks to
the west during La Niña. The El Niño Southern Oscillation (ENSO) is the coupled ocean-atmosphere process that includes both El Niño and La Niña. (Source: Geofile 569)
See NASA's Earth Observatory website for the impacts of La Nina. Click the link below to have a look.
What is the difference between El Nino and La Nina?
Both terms refer to large-scale changes in sea-surface temperature across the central and eastern tropical Pacific. Usually, sea-surface readings off South America’s west coast range from about 15°C to 21°C, while they exceed 25°C in the ‘warm pool’ located in the central and western Pacific. This warm pool expands to cover the tropics during El Niño, but shrinks to
the west during La Niña. The El Niño Southern Oscillation (ENSO) is the coupled ocean-atmosphere process that includes both El Niño and La Niña. (Source: Geofile 569)
See NASA's Earth Observatory website for the impacts of La Nina. Click the link below to have a look.
4. The impacts of El Nino.
The slideshow below provides a selection of infographics highlighting the impacts around the world.