El Nino and La Niña are opposite phases known as the El Niño-Southern Oscillation (ENSO) cycle. The ENSO is a recurring climatic pattern involving temperature changes in the eastern and central tropical Pacific Ocean's waters. It changes in the patterns of upper and lower-level winds, sea-level pressure, and tropical rainfall across the Pacific Basin.
El Nino is often called the warm phase, and La Nina is called the cold phase of ENSO. These deviations from the normal surface temperatures can have a large-scale impact on the global weather conditions and overall climate.
The phrase “El Niño” referred to the Christ Child and was coined by fishermen along the coasts of Ecuador and Peru to describe the warming of the central and eastern Pacific.
This cross-section of the Pacific Ocean, along the equator, illustrates atmospheric circulation pattern typically found at the equatorial Pacific. Note the position of the thermocline.
Only El Nino = [Warm water in Eastern Pacific + Coldwater in Western Pacific].
Only SO = [Low Pressure over Eastern Pacific + High Pressure over Western Pacific]
ENSO = [Warm water in Eastern Pacific + Low Pressure over Eastern Pacific] + [Cold water in Western Pacific + High Pressure over Western Pacific].
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El Nino, La Nina , ENSO
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Some of the other weather effects of La Niña include
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