EXPLANATION TEXT

The converse of the Niño effect is the La Niña effect, which is an exaggeration of normal conditions. This takes place when trade winds blow strongly and consistently across the Pacific towards Australia. This pushes the warm waters from the central Pacific, off the northern Australian coast, to build up into a mass that is bigger than normal.

The El Niño and La Niña Phenomena

Deviations from normal temperature patterns of the southern Pacific Ocean, between Australia and South America, result in the phenomenon called El Niño. Under normal conditions, eastern trade winds blows across the Pacific. These drive the sun-warmed surface water from the central Pacific to the coast of northern Australia. When clouds form above this area of warm water and move over Indonesia, Papua New Guinea, and Australia, they bring rain with them. Every two to seven years, however, this pattern is interrupted by the El Niño event. During El Niño, the Pacific Ocean of Australia does not warm as much as it normally does. Instead, it becomes warmer right up to the coast of Peru in South America. At the same time, the easterly trade winds that blow across the Pacific reverse their direction. This causes high-pressure systems to build up to the north of and across the Australian Continent, preventing moist tropical air reaching the continent. These conditions in turn result in storms, and in rain falling in the eastern Pacific Ocean and in South America instead of in Australia, Papua New Guinea, and Indonesia, which suffer drought conditions.

While the effect of El Niño are sometimes weak, at the other times they are very strong. During a severe El Niño period, extreme drought conditions prevail, as in 1982–83 and 1997-98. In contrast, heavy rainfall and flooding occurred in parts of North and South America. In 1997, there were severe storms and floods in Mexico and further north along the west coast of the United States.

The converse of the El Niño effect is the La Niña effect, which is an exaggeration of normal conditions. This takes place when trade winds blow strongly and consistently across the Pacific towards Australia. This pushes the warm waters from the central Pacific, off the northern Australian coast, to build up into a mass that is bigger than normal. Thus, much more cloud develops than usual, and this brings considerably more rain to Australia and neighboring countries.

Taken from Geographica’s Pocket World Reference, 2007

Answer the questions!

1.      What cause the El Niño phenomenon?

2.      Explain how rain falls in Indonesia, Papua New Guinea, and Australia.

3.      Explain why Australia, Papua New Guinea and Indonesia suffer drought conditions during El Niño year.

4.      What natural disasters did Mexico suffer in 1997 as the result of El Niño?

5.      Explain how La Niña effect takes place.

 

The El Niño Phenomenon

What Is El Niño?

El Niño is a warm water current which moves off the west coast of Chile and Peru. The current is believed to be closely associated with irregular variations in the global weather system and it occurs approximately every 7–11years. The wider consequences of El Niño can be atastrophic. The current is associated with short–term changes in worldwide climate patterns, and may cause drought in place such as Australia and violent tropical cyclones in the Pacific Ocean. Some scientists fear that global warming may be making El Niño occur more frequently.

How Does El Niño Occur?

The combined influence of land, sea and air on weather conditions can create a global climate rhythm. In the Pacific Ocean, for example (A), trade winds normally blow from east to west (1) along the Equator, "dragging" sun–warmed surface waters into a pool of North Australia and there by the thermocline–the boundary between warm surface waters and the cooler layers beneath (2). High cumulus clouds form above these warm waters, bringing rain in the summer wet season (3). Cooler, nutrient-rich waters rise to surface off Southern America (4). supporting extensive shoals of anchovies on which a vast fishing industry has developed. The weather over this cold water region is dry.

Every 3–5 years a change occurs in the ocean-atmosphere interaction. The climatic pattern is reserved (B)–an event known as El Niño. The trade winds ease, or even reverse direction (5). during El Niño and the warm surface waters which have "pulled up" in the West Pacific flow back to warm the waters off South America by 2–3°C (6). This depresses the east thermocline (7) and dramatically affects the climate. In an El Niño year, drought and bush fires occur over Australia, while flood affect Bolivia and Peru. The warm waters off South America suppress upwelling of the cold nutrient rich waters, bringing disaster to the fishing industry.

Taken from Philip’s Science and Technology

Encyclopedia, 1998

Work in pairs. Discuss the text you have just read.

Then rewrite it in your own words.

The Structure of the Text

• General Statement

What is El Niño?

• Explanation

How does El Niño occur?