El Nino and Climate Prediction

El Nino rearrranges the distribution of rainfall in the equatorial Pacific. During normal years (top figure) upwelling induced by the esterly surface winds along the equator (arrow) keeps the surface waters of the central Pacific cool (blue). Heavy rainfall is confined to the warm (red) waters surrounding Indonesia at the western end of the Pacific.

During El Nino (bottom) the easterly surface winds weaken and retreat to the eastern Pacific, allowing the central Pacific to warm, and the rain area to migrate westward.

Below is a more detailed view of ow El Nino rearranges the distribution of rainfall over the tropical Pacific. The colors indicate the distribution of sea-surface temperatue for the cold month of November 1988 and the warm (El nino) month of November 1982, the same months for which the pressure patterns are shown on p.9. red indicates warmer water, and blue indicates colder water. The regions of heavy rainfall is viewed by satellite are indicated by the clouds. The surface winds on the equator are indicated by the arrows. note how tropical rainfall was supressed wherever the sea-surface temperatures were lower than about 80 degrees-F (bluer colors).