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Selected text from: CPC ENSO Main Page

In the tropical Pacific, trade winds generally drive the surface waters westward. The surface water becomes progressively warmer going westward because of its longer exposure to solar heating. El Niño is observed when the easterly trade winds weaken, allowing warmer waters of the western Pacific to mi

This is why during most non El Niño Years, heavy rainfall is found over the warmer waters of the western Pacific (near Indonesia) while the eastern Pacific is relatively dry.

Simultaneously, the deepening of the winter upper-level trough (typically found over the eastern US) produced heavier than normal rains in the southern states (blue shading).

The easterly trade winds of the tropics drag the surface waters of the eastern Pacific away from the coastlines of the Americas. As it moves away, the water is deflected northward (in the northern hemisphere) by the Coriolis force and southward (in the southern hemisphere), causing water to move away from the equator in both directions. Upwelling in the eastern Pacific brings colder water up from deeper levels to replace the surface water that has been dragged away.

grate eastward and eventually reach the South American Coast (shown in orange). The cool nutrient-rich sea water normally found along the coast of Peru is replaced by warmer water depleted of nutrients, resulting in a dramatic reduction in marine fish and plant life.

Some topics in this essay:
El Niño, Niño Events, South American, Mauritania Somalia, December SSTs, La Niña, American Coast, el niño, Plains United, Main Page, South America, trade winds, surface water, eastern pacific, western pacific, el niño event, niño event, warmer waters, easterly trade, tropical pacific, easterly trade winds, eastern tropical pacific, niño events, el niño events, trade winds weaken,