Chapter 14 - Equatorial Processes

14.6 Important Concepts

1. Equatorial processes are important because heat released by rain in the equatorial region drives an important part of the atmospheric circulation.



2. Equatorial currents redistribute heat. The interannual variability of currents and temperatures in the equatorial Pacific modulates the oceanic forcing of the atmosphere.



3. Changes in equatorial dynamics cause changes in atmospheric circulation.



4. El Niño causes the biggest changes in equatorial dynamics. During El Niño, trade-winds weaken in the western Pacific, the thermocline becomes less deep in the west. This drives a Kelvin wave eastward along the equator, which deepens the thermocline in the eastern Pacific. The warm pool in the west moves eastward toward the central Pacific, and the intense tropical rain areas move with the warm pool.



5. As a result of El Niño, drought occurs in the Indonesian area and northern Australia, and floods occur in western, tropical South America. Variations in the atmospheric circulation influence more distant areas through teleconnections.



6. Forecasts of El Niño are made using coupled ocean-atmospheric numerical models. Forecasts appear to have useful accuracy for 3–6 months in advance, mostly after the onset of El Niño.

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