During an El Niño or La Niña, the changes in Pacific Ocean temperatures affect the patterns of tropical rainfall from Indonesia to the west coast of South America, a distance covering approximately one-half way around the world.
These changes in tropical rainfall affect weather patterns throughout the world.
During El Nino, rainfall and thunderstorm activity diminishes over the western equatorial Pacific, and increases over the eastern half of the tropical Pacific.
This area of increased rainfall occurs where the exceptionally warm ocean waters have reached about 28°C or 82°F.
This overall pattern of rainfall departures spans nearly one-half the distance around the globe, and is responsible for many of the global weather impacts caused by El Niño.
During La Niña, rainfall and thunderstorm activity diminishes over the central equatorial Pacific, and becomes confined to Indonesia and the western Pacific.
The area experiencing a reduction in rainfall generally coincides quite well with the area of abnormally cold ocean surface temperatures.
This overall pattern of rainfall departures spans nearly one-half the way around the globe, and is responsible for many of the global weather impacts caused by La Nina.
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