What Is An El Nino?

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An EJ Nifte is a temporary change in the climate of the Pacific Ocean, in the region around the equator. You can see its effects in both the ocean and atmosphere, generally in Northern Hemisphere winter. Typically, the ocean surface warms up by a few degrees Celsius. At the same time, the place where hefty thunderstorms Replica Omega occur on the equator moves eastward. Although those might seem like small differences, it nevertheless can have big effects on the world's climate.
What causes it?

Usually, the wind blows strongly from east to west along the equator in the Pacific. This actually piles up water (about half a meter's worth) in the western part of the Pacific. In the eastern part, deeper water (which is colder than the sun-warmed surface water) gets pulled up from below to replace the water pushed west. So, the normal situation is warm water (about 30X3) in the west, cold (about 22X3) in the east.

In an El Nino, the winds pushing that water around get weaker. As a result, some of the warm water piled up in the west ...
... slumps back down to the east, and not as much cold water gets pulled up from below. Both these tend to make the water in the eastern Pacific warmer, which is one of the hallmarks of an El Nino.

But it doesn't stop there. The warmer ocean then affects the winds--it makes the winds weaker! So if the winds get weaker, then the ocean gets winner, which makes the winds get weaker, which makes the ocean get warmer? This is called a positive feedback, and is what makes an El Nino grow.

What effects does it have?

A strong El Nino is often associated with wet winters over the southern US, as well as drought in Indonesia and Australia. Keep in mind that you're not guaranteed these effects even though there is an El Nino going on; but the El Nino does make these effects more likely to happen.
How long does it last?

A strong El Nino can last a year or more before conditions return to normal. If you read the bit above about Rossby and Kelvin waves (you did, didn't t you?), then you know that it lasts more or less as long as it takes the interior-ocean waves to travel all the way over to the coast of Asia, get reflected, and travel back.

How often do we get them?

El Nino happens irregularly, but if you want to impress people at cocktail parties, you might mention that we usually get one every three to seven years. Note the word "usually"; some?times they turn up more frequently, sometimes less.

How well can we predict El Nino?

On average, complex computer models designed to predict El Nino can successfully do so 12 to 18 months in advance. However, it seems to vary by episode; sometimes El Ninos are predicted quite well, with plenty of advance notice Tag Heuer Replica Watches from the models, while other times they are predicted poorly, with the models not picking them up until the El Nino has already started. Trying to fix up the models is one of our research topics here at Scripps.