Лекция: El Nino

The ocean is a thin, spherical shell of fluid on a rotating sphere and, in addition to the waves seen on the ocean surface when the wind is blowing, there are other waves that have a large amplitude, not at the surface, but along the subsurface thermocline. Some are confined to the neighborhood of the equator where they travel exceptionally fast. Because of those waves, warm surface waters can be redistributed along the equator far more rap­idly than is possible at higher latitudes, which is why large-scale changes in sea surface temperature patterns, associated with a hori­zontal redistribution of upper ocean water, occur more readily in the tropics than in higher latitudes. Such an occurrence that leads to high sea surface temperatures in the eastern tropical Pacific is known as El Nino. The interval between El Nino episodes, three years approx­imately, depends on the time it takes the waves to propagate across the basin and hence depends on the width of the Pacific.

EL Nino affects everyone, either directly because of its influence on climate and weather, or indirectly because of its influence on the global economy. The impact of this phenomenon can be: devastating floods in Ecuador and Peru, where a warming of the surface waters of the eastern tropical Pacific – the signature of El Nino – is associated with the disappearance of the usually abundant fish; disastrous droughts in the «maritime» continent of southeastern Asia and northern Australia; unusual weather patterns over North and South America; poor mon­soons over India; and low rainfall over southeastern Africa.

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