Notes

EL NINO Y LA NINA AFFECTIONS

- During El Niño, New Zealand tends to experience stronger or more frequent winds from the west in summer, typically leading to drought in east coast areas and more rain in the west. In winter, the winds tend to be more from the south, bringing colder conditions to both the land and the surrounding ocean. In spring and autumn, south-westerly winds are more common.

- El Niño is a natural feature of the global climate system. Originally it was the name given to the periodic development of unusually warm ocean waters along the tropical South American coast and out along the Equator to the dateline, but now it is more generally used to describe the whole "El Niño - Southern Oscillation (ENSO) phenomenon", the major systematic global climate fluctuation that occurs at the time of the ocean warming event. El Niño and La Niña refer to opposite extremes of the ENSO cycle when major changes in the Pacific atmospheric and oceanic circulation occur.

- During El Niño, the trade winds weaken, leading to a rise in sea surface temperature in the eastern equatorial Pacific and a reduction of upwelling off South America. Heavy rainfall and flooding occur over Peru and drought over Indonesia and Australia. The supplies of nutrient-rich water off the South American coast are cut off due to the reduced upwelling, adversely affecting fisheries in that region. In the tropical South Pacific, the pattern of occurrence of tropical cyclones shifts eastward, so there are more cyclones than normal in areas such as the Cook Islands and French Polynesia.

- When neither El Niño nor La Niña is present, (usually referred to as "neutral" or normal conditions), trade winds blow westward across the Pacific, piling up warm surface water so that Indonesian sea levels are about 50 cm higher than those in Ecuador. Cool, nutrient-rich seawater "wells up" off the South American coast, supporting marine ecosystems and fisheries. Relatively cold sea temperatures also extend along the equator from South America towards the central Pacific. High rainfall occurs in the rising air over the warmest water to the west, whereas the colder east Pacific is relatively dry.

- When neither El Niño nor La Niña is present, (usually referred to as "neutral" or normal conditions), trade winds blow westward across the Pacific, piling up warm surface water so that Indonesian sea levels are about 50 cm higher than those in Ecuador. Cool, nutrient-rich seawater "wells up" off the South American coast, supporting marine ecosystems and fisheries. Relatively cold sea temperatures also extend along the equator from South America towards the central Pacific. High rainfall occurs in the rising air over the warmest water to the west, whereas the colder east Pacific is relatively dry.