What are the El-Nino and El Nina?
ENSO (El Nino – Southern Oscillation) is best defined by a multivariate ENSO index that is > 0, while La Nina would be <0. Since we're never precisely at 0, except due to limitations in our ability to measure and define, we're always in either an El Nino or La Nina condition. In normal, non-El Nino conditions, the trade winds blow towards the west across the tropical Pacific. These winds pile up warm surface water in the west Pacific, so that the sea surface is about 1/2 meter higher at Indonesia than at Ecuador. The sea surface temperature is about 8 degrees C higher in the west, with cool temperatures off South America, due to an upwelling of cold water from deeper levels. This cold water is nutrient-rich, supporting high levels of primary productivity, diverse marine ecosystems, and major fisheries. Rainfall is found in rising air over the warmest water, and the east Pacific is relatively dry. During El Nino, the trade winds relax in the central and western Pacific leading to a depr
