El Nino Essay

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El Nino

Typically, the level of ocean water around the world is higher in the western Pacific and lower in the eastern, near the Western coast of South and
North America. This is due primarily to the presence of easterly winds in the
Pacific, which drag the surface water westward and raise the thermocline relatively all the way up to the surface in the east and dampen it in the west.
During El Nino conditions, however, the easterlies move east, reducing the continuing interaction between wind and sea, allowing the thermocline to become nearly flat and to plunge several feet below the surface of the water, allowing the water to grow warm and expand. With the help of the National Oceanic and
Atmospheric …show more content…

Where the surface water moves away, colder, nutrient-rich water comes up from below to replace it which is called upwelling. The winds that blow along the equator also affect the properties of upwelled water. When there is no wind, the dividing layer between the warm surface water and the deep cold water would be almost flat; but the winds drag the surface water westward, raising the thermocline nearly all the way up to the surface in the east and depressing in the west.
The resulting changes in sea-surface temperature will have an effect on the winds. When the easterlies are blowing at full strength, the upwelling of cold water along the equatorial Pacific chills the air above it, making it too dense to rise high enough for water vapor to condense to form clouds and raindrops. As a result, this part of the ocean stays indubitably free of clouds during normal years and the rain in the equatorial belt is mostly confined to the extreme western Pacific. However, when the easterlies weaken and retreat eastward during the early stages of an El Nino event, the upwelling slows and the ocean warms.
The moist air above also warms. It would produce deep clouds which make heavy rain along the equator. The change in ocean temperatures thus causes the major rain zone over the western Pacific to shift eastward. In this way, the dialogue between wind and sea in the Pacific can become more and more

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