f98u2le6 - Lesson VI. El Nio The goal of this unit is to...

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Lesson VI. El Niño The goal of this unit is to explain the weather phenomenon El Niño, its causes and effects. Keywords: El Niño, trade winds, Global Positioning System Satellites: El Niño Watched from Space TOPEX/Poseidon Initial Science Results Source:http://www.csr.utexas.edu/tsgc/topex/results.html NASA’s space-borne sensors help to monitor global climate changes. In the context of climate and weather, the name El Niño originally referred to the warm ocean current that appears along the Pacific coast of South America every year around Christmas. In Spanish, “El Niño” means “the boy,” a reference to the Christ child, since historically the phenomenon has been observed around Christmas. Recently, however, the term has been applied to those years when there is a change in this annual pattern. In the equatorial Pacific Ocean, the wind usually blows from east to west, dragging the surface water along. Because of Earth’s rotation, the eastward-flowing water is deflected to the north in the Northern Hemisphere and to the south in the Southern Hemisphere. This creates a surface divergence along the equator that is filled by cold, nutrient-rich water moving up from below (upwelling), forming a cold tongue in the eastern Pacific. As the warmer surface water is moved westward by wind, the thermocline (a zone in the water column that shows a sudden change in temperature with depth) separating the surface water from the colder water is raised in the east and depressed in the west. The easterly wind converges over the resulting warm water in the western Pacific, picks up large amounts of moisture and ascends through the atmosphere by a process known as deep convection.
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Dry air subsides above the cold tongue and forms the Walker Circulation along the equator. The easterly wind retreats and the westerly wind pushes the convection process to
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f98u2le6 - Lesson VI. El Nio The goal of this unit is to...

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